a class to store JSON values More...
#include <json.hpp>
Collaboration diagram for nlohmann::basic_json< ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType >:Classes | |
| class | const_iterator |
| a const random access iterator for the basic_json class More... | |
| class | iterator |
| a mutable random access iterator for the basic_json class More... | |
| class | json_reverse_iterator |
| a template for a reverse iterator class More... | |
Public Types | |
| enum | value_t : uint8_t { value_t::null, value_t::object, value_t::array, value_t::string, value_t::boolean, value_t::number_integer, value_t::number_unsigned, value_t::number_float, value_t::discarded } |
| the JSON type enumeration More... | |
| enum | parse_event_t : uint8_t { parse_event_t::object_start, parse_event_t::object_end, parse_event_t::array_start, parse_event_t::array_end, parse_event_t::key, parse_event_t::value } |
| JSON callback events. More... | |
| using | parser_callback_t = std::function< bool(int depth, parse_event_t event, basic_json &parsed)> |
| per-element parser callback type More... | |
Static Public Member Functions | |
| static allocator_type | get_allocator () |
| returns the allocator associated with the container | |
container types | |
| using | value_type = basic_json |
| the type of elements in a basic_json container | |
| using | reference = value_type & |
| the type of an element reference | |
| using | const_reference = const value_type & |
| the type of an element const reference | |
| using | difference_type = std::ptrdiff_t |
| a type to represent differences between iterators | |
| using | size_type = std::size_t |
| a type to represent container sizes | |
| using | allocator_type = AllocatorType< basic_json > |
| the allocator type | |
| using | pointer = typename std::allocator_traits< allocator_type >::pointer |
| the type of an element pointer | |
| using | const_pointer = typename std::allocator_traits< allocator_type >::const_pointer |
| the type of an element const pointer | |
| using | reverse_iterator = json_reverse_iterator< typename basic_json::iterator > |
| a reverse iterator for a basic_json container | |
| using | const_reverse_iterator = json_reverse_iterator< typename basic_json::const_iterator > |
| a const reverse iterator for a basic_json container | |
JSON value data types | |
| using | object_t = ObjectType< StringType, basic_json, std::less< StringType >, AllocatorType< std::pair< const StringType, basic_json >>> |
| a type for an object More... | |
| using | array_t = ArrayType< basic_json, AllocatorType< basic_json >> |
| a type for an array More... | |
| using | string_t = StringType |
| a type for a string More... | |
| using | boolean_t = BooleanType |
| a type for a boolean More... | |
| using | number_integer_t = NumberIntegerType |
| a type for a number (integer) More... | |
| using | number_unsigned_t = NumberUnsignedType |
| a type for a number (unsigned) More... | |
| using | number_float_t = NumberFloatType |
| a type for a number (floating-point) More... | |
constructors and destructors | |
| static basic_json | array (std::initializer_list< basic_json > init=std::initializer_list< basic_json >()) |
| explicitly create an array from an initializer list More... | |
| static basic_json | object (std::initializer_list< basic_json > init=std::initializer_list< basic_json >()) |
| explicitly create an object from an initializer list More... | |
| basic_json (const value_t value_type) | |
| create an empty value with a given type More... | |
| basic_json ()=default | |
| create a null object (implicitly) More... | |
| basic_json (std::nullptr_t) noexcept | |
| create a null object (explicitly) More... | |
| basic_json (const object_t &val) | |
| create an object (explicit) More... | |
| template<class CompatibleObjectType , typename std::enable_if< std::is_constructible< typename object_t::key_type, typename CompatibleObjectType::key_type >::value andstd::is_constructible< basic_json, typename CompatibleObjectType::mapped_type >::value, int >::type = 0> | |
| basic_json (const CompatibleObjectType &val) | |
| create an object (implicit) More... | |
| basic_json (const array_t &val) | |
| create an array (explicit) More... | |
| template<class CompatibleArrayType , typename std::enable_if< not std::is_same< CompatibleArrayType, typename basic_json_t::iterator >::value andnot std::is_same< CompatibleArrayType, typename basic_json_t::const_iterator >::value andnot std::is_same< CompatibleArrayType, typename basic_json_t::reverse_iterator >::value andnot std::is_same< CompatibleArrayType, typename basic_json_t::const_reverse_iterator >::value andnot std::is_same< CompatibleArrayType, typename array_t::iterator >::value andnot std::is_same< CompatibleArrayType, typename array_t::const_iterator >::value andstd::is_constructible< basic_json, typename CompatibleArrayType::value_type >::value, int >::type = 0> | |
| basic_json (const CompatibleArrayType &val) | |
| create an array (implicit) More... | |
| basic_json (const string_t &val) | |
| create a string (explicit) More... | |
| basic_json (const typename string_t::value_type *val) | |
| create a string (explicit) More... | |
| template<class CompatibleStringType , typename std::enable_if< std::is_constructible< string_t, CompatibleStringType >::value, int >::type = 0> | |
| basic_json (const CompatibleStringType &val) | |
| create a string (implicit) More... | |
| basic_json (boolean_t val) noexcept | |
| create a boolean (explicit) More... | |
| template<typename T , typename std::enable_if< not(std::is_same< T, int >::value) and std::is_same< T, number_integer_t >::value, int >::type = 0> | |
| basic_json (const number_integer_t val) noexcept | |
| create an integer number (explicit) More... | |
| basic_json (const int val) noexcept | |
| create an integer number from an enum type (explicit) More... | |
| template<typename CompatibleNumberIntegerType , typename std::enable_if< std::is_constructible< number_integer_t, CompatibleNumberIntegerType >::value andstd::numeric_limits< CompatibleNumberIntegerType >::is_integer andstd::numeric_limits< CompatibleNumberIntegerType >::is_signed, CompatibleNumberIntegerType >::type = 0> | |
| basic_json (const CompatibleNumberIntegerType val) noexcept | |
| create an integer number (implicit) More... | |
| template<typename T , typename std::enable_if< not(std::is_same< T, int >::value) and std::is_same< T, number_unsigned_t >::value, int >::type = 0> | |
| basic_json (const number_unsigned_t val) noexcept | |
| create an unsigned integer number (explicit) More... | |
| template<typename CompatibleNumberUnsignedType , typename std::enable_if< std::is_constructible< number_unsigned_t, CompatibleNumberUnsignedType >::value andstd::numeric_limits< CompatibleNumberUnsignedType >::is_integer and!std::numeric_limits< CompatibleNumberUnsignedType >::is_signed, CompatibleNumberUnsignedType >::type = 0> | |
| basic_json (const CompatibleNumberUnsignedType val) noexcept | |
| create an unsigned number (implicit) More... | |
| basic_json (const number_float_t val) noexcept | |
| create a floating-point number (explicit) More... | |
| template<typename CompatibleNumberFloatType , typename = typename std::enable_if< std::is_constructible<number_float_t, CompatibleNumberFloatType>::value and std::is_floating_point<CompatibleNumberFloatType>::value>::type> | |
| basic_json (const CompatibleNumberFloatType val) noexcept | |
| create an floating-point number (implicit) More... | |
| basic_json (std::initializer_list< basic_json > init, bool type_deduction=true, value_t manual_type=value_t::array) | |
| create a container (array or object) from an initializer list More... | |
| basic_json (size_type cnt, const basic_json &val) | |
| construct an array with count copies of given value More... | |
| template<class InputIT , typename std::enable_if< std::is_same< InputIT, typename basic_json_t::iterator >::value orstd::is_same< InputIT, typename basic_json_t::const_iterator >::value, int >::type = 0> | |
| basic_json (InputIT first, InputIT last) | |
| construct a JSON container given an iterator range More... | |
| basic_json (std::istream &i, parser_callback_t cb=nullptr) | |
| construct a JSON value given an input stream More... | |
| basic_json (const basic_json &other) | |
| copy constructor More... | |
| basic_json (basic_json &&other) noexcept | |
| move constructor More... | |
| reference & | operator= (basic_json other) noexcept(std::is_nothrow_move_constructible< value_t >::value andstd::is_nothrow_move_assignable< value_t >::value andstd::is_nothrow_move_constructible< json_value >::value andstd::is_nothrow_move_assignable< json_value >::value) |
| copy assignment More... | |
| ~basic_json () | |
| destructor More... | |
object inspection | |
| string_t | dump (const int indent=-1) const |
| serialization More... | |
| constexpr value_t | type () const noexcept |
| return the type of the JSON value (explicit) More... | |
| constexpr bool | is_primitive () const noexcept |
| return whether type is primitive More... | |
| constexpr bool | is_structured () const noexcept |
| return whether type is structured More... | |
| constexpr bool | is_null () const noexcept |
| return whether value is null More... | |
| constexpr bool | is_boolean () const noexcept |
| return whether value is a boolean More... | |
| constexpr bool | is_number () const noexcept |
| return whether value is a number More... | |
| constexpr bool | is_number_integer () const noexcept |
| return whether value is an integer number More... | |
| constexpr bool | is_number_unsigned () const noexcept |
| return whether value is an unsigned integer number More... | |
| constexpr bool | is_number_float () const noexcept |
| return whether value is a floating-point number More... | |
| constexpr bool | is_object () const noexcept |
| return whether value is an object More... | |
| constexpr bool | is_array () const noexcept |
| return whether value is an array More... | |
| constexpr bool | is_string () const noexcept |
| return whether value is a string More... | |
| constexpr bool | is_discarded () const noexcept |
| return whether value is discarded More... | |
| constexpr | operator value_t () const noexcept |
| return the type of the JSON value (implicit) More... | |
value access | |
| template<typename ValueType , typename std::enable_if< not std::is_pointer< ValueType >::value, int >::type = 0> | |
| ValueType | get () const |
| get a value (explicit) More... | |
| template<typename PointerType , typename std::enable_if< std::is_pointer< PointerType >::value, int >::type = 0> | |
| PointerType | get () noexcept |
| get a pointer value (explicit) More... | |
| template<typename PointerType , typename std::enable_if< std::is_pointer< PointerType >::value, int >::type = 0> | |
| constexpr const PointerType | get () const noexcept |
| get a pointer value (explicit) More... | |
| template<typename PointerType , typename std::enable_if< std::is_pointer< PointerType >::value, int >::type = 0> | |
| PointerType | get_ptr () noexcept |
| get a pointer value (implicit) More... | |
| template<typename PointerType , typename std::enable_if< std::is_pointer< PointerType >::valueand std::is_const< typename std::remove_pointer< PointerType >::type >::value, int >::type = 0> | |
| constexpr const PointerType | get_ptr () const noexcept |
| get a pointer value (implicit) More... | |
| template<typename ReferenceType , typename std::enable_if< std::is_reference< ReferenceType >::value, int >::type = 0> | |
| ReferenceType | get_ref () |
| get a reference value (implicit) More... | |
| template<typename ReferenceType , typename std::enable_if< std::is_reference< ReferenceType >::valueand std::is_const< typename std::remove_reference< ReferenceType >::type >::value, int >::type = 0> | |
| ReferenceType | get_ref () const |
| get a reference value (implicit) More... | |
| template<typename ValueType , typename std::enable_if< not std::is_pointer< ValueType >::valueand not std::is_same< ValueType, typename string_t::value_type >::valueand not std::is_same< ValueType, std::initializer_list< typename string_t::value_type >>::value, int >::type = 0> | |
| operator ValueType () const | |
| get a value (implicit) More... | |
element access | |
| reference | at (size_type idx) |
| access specified array element with bounds checking More... | |
| const_reference | at (size_type idx) const |
| access specified array element with bounds checking More... | |
| reference | at (const typename object_t::key_type &key) |
| access specified object element with bounds checking More... | |
| const_reference | at (const typename object_t::key_type &key) const |
| access specified object element with bounds checking More... | |
| reference | operator[] (size_type idx) |
| access specified array element More... | |
| const_reference | operator[] (size_type idx) const |
| access specified array element More... | |
| reference | operator[] (const typename object_t::key_type &key) |
| access specified object element More... | |
| const_reference | operator[] (const typename object_t::key_type &key) const |
| read-only access specified object element More... | |
| template<typename T , std::size_t n> | |
| reference | operator[] (T *(&key)[n]) |
| access specified object element More... | |
| template<typename T , std::size_t n> | |
| const_reference | operator[] (T *(&key)[n]) const |
| read-only access specified object element More... | |
| template<typename T > | |
| reference | operator[] (T *key) |
| access specified object element More... | |
| template<typename T > | |
| const_reference | operator[] (T *key) const |
| read-only access specified object element More... | |
| template<class ValueType , typename std::enable_if< std::is_convertible< basic_json_t, ValueType >::value, int >::type = 0> | |
| ValueType | value (const typename object_t::key_type &key, ValueType default_value) const |
| access specified object element with default value More... | |
| string_t | value (const typename object_t::key_type &key, const char *default_value) const |
| overload for a default value of type const char* More... | |
| reference | front () |
| access the first element More... | |
| const_reference | front () const |
| access the first element More... | |
| reference | back () |
| access the last element More... | |
| const_reference | back () const |
| access the last element More... | |
| template<class InteratorType , typename std::enable_if< std::is_same< InteratorType, typename basic_json_t::iterator >::value orstd::is_same< InteratorType, typename basic_json_t::const_iterator >::value, int >::type = 0> | |
| InteratorType | erase (InteratorType pos) |
| remove element given an iterator More... | |
| template<class InteratorType , typename std::enable_if< std::is_same< InteratorType, typename basic_json_t::iterator >::value orstd::is_same< InteratorType, typename basic_json_t::const_iterator >::value, int >::type = 0> | |
| InteratorType | erase (InteratorType first, InteratorType last) |
| remove elements given an iterator range More... | |
| size_type | erase (const typename object_t::key_type &key) |
| remove element from a JSON object given a key More... | |
| void | erase (const size_type idx) |
| remove element from a JSON array given an index More... | |
lookup | |
| iterator | find (typename object_t::key_type key) |
| find an element in a JSON object More... | |
| const_iterator | find (typename object_t::key_type key) const |
| find an element in a JSON object More... | |
| size_type | count (typename object_t::key_type key) const |
| returns the number of occurrences of a key in a JSON object More... | |
iterators | |
| static iteration_proxy< iterator > | iterator_wrapper (reference cont) |
| wrapper to access iterator member functions in range-based for More... | |
| static iteration_proxy < const_iterator > | iterator_wrapper (const_reference cont) |
| wrapper to access iterator member functions in range-based for More... | |
| iterator | begin () noexcept |
| returns an iterator to the first element More... | |
| const_iterator | begin () const noexcept |
| returns a const iterator to the first element More... | |
| const_iterator | cbegin () const noexcept |
| returns a const iterator to the first element More... | |
| iterator | end () noexcept |
| returns an iterator to one past the last element More... | |
| const_iterator | end () const noexcept |
| returns a const iterator to one past the last element More... | |
| const_iterator | cend () const noexcept |
| returns a const iterator to one past the last element More... | |
| reverse_iterator | rbegin () noexcept |
| returns an iterator to the reverse-beginning More... | |
| const_reverse_iterator | rbegin () const noexcept |
| returns a const reverse iterator to the last element More... | |
| reverse_iterator | rend () noexcept |
| returns an iterator to the reverse-end More... | |
| const_reverse_iterator | rend () const noexcept |
| returns a const reverse iterator to one before the first More... | |
| const_reverse_iterator | crbegin () const noexcept |
| returns a const reverse iterator to the last element More... | |
| const_reverse_iterator | crend () const noexcept |
| returns a const reverse iterator to one before the first More... | |
capacity | |
| bool | empty () const noexcept |
| checks whether the container is empty More... | |
| size_type | size () const noexcept |
| returns the number of elements More... | |
| size_type | max_size () const noexcept |
| returns the maximum possible number of elements More... | |
modifiers | |
| void | clear () noexcept |
| clears the contents More... | |
| void | push_back (basic_json &&val) |
| add an object to an array More... | |
| reference | operator+= (basic_json &&val) |
| add an object to an array More... | |
| void | push_back (const basic_json &val) |
| add an object to an array More... | |
| reference | operator+= (const basic_json &val) |
| add an object to an array More... | |
| void | push_back (const typename object_t::value_type &val) |
| add an object to an object More... | |
| reference | operator+= (const typename object_t::value_type &val) |
| add an object to an object More... | |
| iterator | insert (const_iterator pos, const basic_json &val) |
| inserts element More... | |
| iterator | insert (const_iterator pos, basic_json &&val) |
| inserts element More... | |
| iterator | insert (const_iterator pos, size_type cnt, const basic_json &val) |
| inserts elements More... | |
| iterator | insert (const_iterator pos, const_iterator first, const_iterator last) |
| inserts elements More... | |
| iterator | insert (const_iterator pos, std::initializer_list< basic_json > ilist) |
| inserts elements More... | |
| void | swap (reference other) noexcept(std::is_nothrow_move_constructible< value_t >::value andstd::is_nothrow_move_assignable< value_t >::value andstd::is_nothrow_move_constructible< json_value >::value andstd::is_nothrow_move_assignable< json_value >::value) |
| exchanges the values More... | |
| void | swap (array_t &other) |
| exchanges the values More... | |
| void | swap (object_t &other) |
| exchanges the values More... | |
| void | swap (string_t &other) |
| exchanges the values More... | |
lexicographical comparison operators | |
| bool | operator< (const value_t lhs, const value_t rhs) noexcept |
| comparison operator for JSON types More... | |
| bool | operator== (const_reference lhs, const_reference rhs) noexcept |
| comparison: equal More... | |
| bool | operator== (const_reference v, std::nullptr_t) noexcept |
| comparison: equal More... | |
| bool | operator== (std::nullptr_t, const_reference v) noexcept |
| comparison: equal More... | |
| bool | operator!= (const_reference lhs, const_reference rhs) noexcept |
| comparison: not equal More... | |
| bool | operator!= (const_reference v, std::nullptr_t) noexcept |
| comparison: not equal More... | |
| bool | operator!= (std::nullptr_t, const_reference v) noexcept |
| comparison: not equal More... | |
| bool | operator< (const_reference lhs, const_reference rhs) noexcept |
| comparison: less than More... | |
| bool | operator<= (const_reference lhs, const_reference rhs) noexcept |
| comparison: less than or equal More... | |
| bool | operator> (const_reference lhs, const_reference rhs) noexcept |
| comparison: greater than More... | |
| bool | operator>= (const_reference lhs, const_reference rhs) noexcept |
| comparison: greater than or equal More... | |
serialization | |
| std::ostream & | operator<< (std::ostream &o, const basic_json &j) |
| serialize to stream More... | |
| std::ostream & | operator>> (const basic_json &j, std::ostream &o) |
| serialize to stream More... | |
deserialization | |
| static basic_json | parse (const string_t &s, parser_callback_t cb=nullptr) |
| deserialize from string More... | |
| static basic_json | parse (std::istream &i, parser_callback_t cb=nullptr) |
| deserialize from stream More... | |
| static basic_json | parse (std::istream &&i, parser_callback_t cb=nullptr) |
| deserialize from stream More... | |
| std::istream & | operator<< (basic_json &j, std::istream &i) |
| deserialize from stream More... | |
| std::istream & | operator>> (std::istream &i, basic_json &j) |
| deserialize from stream More... | |
Detailed Description
template<template< typename U, typename V, typename...Args > class ObjectType = std::map, template< typename U, typename...Args > class ArrayType = std::vector, class StringType = std::string, class BooleanType = bool, class NumberIntegerType = std::int64_t, class NumberUnsignedType = std::uint64_t, class NumberFloatType = double, template< typename U > class AllocatorType = std::allocator>
class nlohmann::basic_json< ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType >
a class to store JSON values
- Template Parameters
-
ObjectType type for JSON objects ( std::mapby default; will be used in object_t)ArrayType type for JSON arrays ( std::vectorby default; will be used in array_t)StringType type for JSON strings and object keys ( std::stringby default; will be used in string_t)BooleanType type for JSON booleans ( boolby default; will be used in boolean_t)NumberIntegerType type for JSON integer numbers ( int64_tby default; will be used in number_integer_t)NumberUnsignedType type for JSON unsigned integer numbers ( uint64_tNumberFloatType type for JSON floating-point numbers ( doubleby default; will be used in number_float_t)AllocatorType type of the allocator to use ( std::allocatorby default)
The class satisfies the following concept requirements:
- Basic
- DefaultConstructible: JSON values can be default constructed. The result will be a JSON null value.
- MoveConstructible: A JSON value can be constructed from an rvalue argument.
- CopyConstructible: A JSON value can be copy-constructed from an lvalue expression.
- MoveAssignable: A JSON value van be assigned from an rvalue argument.
- CopyAssignable: A JSON value can be copy-assigned from an lvalue expression.
- Destructible: JSON values can be destructed.
- Layout
- StandardLayoutType: JSON values have standard layout: All non-static data members are private and standard layout types, the class has no virtual functions or (virtual) base classes.
- Library-wide
- EqualityComparable: JSON values can be compared with
==, see operator==(const_reference,const_reference). - LessThanComparable: JSON values can be compared with
<, see operator<(const_reference,const_reference). - Swappable: Any JSON lvalue or rvalue of can be swapped with any lvalue or rvalue of other compatible types, using unqualified function call swap().
- NullablePointer: JSON values can be compared against
std::nullptr_tobjects which are used to model thenullvalue.
- EqualityComparable: JSON values can be compared with
- Container
- Container: JSON values can be used like STL containers and provide iterator access.
- ReversibleContainer; JSON values can be used like STL containers and provide reverse iterator access.
- Since
- version 1.0.0
Member Typedef Documentation
| using nlohmann::basic_json< ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType >::array_t = ArrayType<basic_json, AllocatorType<basic_json>> |
a type for an array
RFC 7159 describes JSON arrays as follows:
An array is an ordered sequence of zero or more values.
To store objects in C++, a type is defined by the template parameters explained below.
- Template Parameters
-
ArrayType container type to store arrays (e.g., std::vectororstd::list)AllocatorType allocator to use for arrays (e.g., std::allocator)
Default type
With the default values for ArrayType (std::vector) and AllocatorType (std::allocator), the default value for array_t is:
Limits
RFC 7159 specifies:
An implementation may set limits on the maximum depth of nesting.
In this class, the array's limit of nesting is not constraint explicitly. However, a maximum depth of nesting may be introduced by the compiler or runtime environment. A theoretical limit can be queried by calling the max_size function of a JSON array.
Storage
Arrays are stored as pointers in a basic_json type. That is, for any access to array values, a pointer of type array_t* must be dereferenced.
- Since
- version 1.0.0
| using nlohmann::basic_json< ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType >::boolean_t = BooleanType |
a type for a boolean
RFC 7159 implicitly describes a boolean as a type which differentiates the two literals true and false.
To store objects in C++, a type is defined by the template parameter BooleanType which chooses the type to use.
Default type
With the default values for BooleanType (bool), the default value for boolean_t is:
Storage
Boolean values are stored directly inside a basic_json type.
- Since
- version 1.0.0
| using nlohmann::basic_json< ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType >::number_float_t = NumberFloatType |
a type for a number (floating-point)
RFC 7159 describes numbers as follows:
The representation of numbers is similar to that used in most programming languages. A number is represented in base 10 using decimal digits. It contains an integer component that may be prefixed with an optional minus sign, which may be followed by a fraction part and/or an exponent part. Leading zeros are not allowed. (...) Numeric values that cannot be represented in the grammar below (such as Infinity and NaN) are not permitted.
This description includes both integer and floating-point numbers. However, C++ allows more precise storage if it is known whether the number is a signed integer, an unsigned integer or a floating-point number. Therefore, three different types, number_integer_t, number_unsigned_t and number_float_t are used.
To store floating-point numbers in C++, a type is defined by the template parameter NumberFloatType which chooses the type to use.
Default type
With the default values for NumberFloatType (double), the default value for number_float_t is:
Default behavior
- The restrictions about leading zeros is not enforced in C++. Instead, leading zeros in floating-point literals will be ignored. Internally, the value will be stored as decimal number. For instance, the C++ floating-point literal
01.2will be serialized to1.2. During deserialization, leading zeros yield an error. - Not-a-number (NaN) values will be serialized to
null.
Limits
RFC 7159 states:
This specification allows implementations to set limits on the range and precision of numbers accepted. Since software that implements IEEE 754-2008 binary64 (double precision) numbers is generally available and widely used, good interoperability can be achieved by implementations that expect no more precision or range than these provide, in the sense that implementations will approximate JSON numbers within the expected precision.
This implementation does exactly follow this approach, as it uses double precision floating-point numbers. Note values smaller than -1.79769313486232e+308 and values greater than 1.79769313486232e+308 will be stored as NaN internally and be serialized to null.
Storage
Floating-point number values are stored directly inside a basic_json type.
- See also
- number_integer_t – type for number values (integer)
- number_unsigned_t – type for number values (unsigned integer)
- Since
- version 1.0.0
| using nlohmann::basic_json< ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType >::number_integer_t = NumberIntegerType |
a type for a number (integer)
RFC 7159 describes numbers as follows:
The representation of numbers is similar to that used in most programming languages. A number is represented in base 10 using decimal digits. It contains an integer component that may be prefixed with an optional minus sign, which may be followed by a fraction part and/or an exponent part. Leading zeros are not allowed. (...) Numeric values that cannot be represented in the grammar below (such as Infinity and NaN) are not permitted.
This description includes both integer and floating-point numbers. However, C++ allows more precise storage if it is known whether the number is a signed integer, an unsigned integer or a floating-point number. Therefore, three different types, number_integer_t, number_unsigned_t and number_float_t are used.
To store integer numbers in C++, a type is defined by the template parameter NumberIntegerType which chooses the type to use.
Default type
With the default values for NumberIntegerType (int64_t), the default value for number_integer_t is:
Default behavior
- The restrictions about leading zeros is not enforced in C++. Instead, leading zeros in integer literals lead to an interpretation as octal number. Internally, the value will be stored as decimal number. For instance, the C++ integer literal
010will be serialized to8. During deserialization, leading zeros yield an error. - Not-a-number (NaN) values will be serialized to
null.
Limits
RFC 7159 specifies:
An implementation may set limits on the range and precision of numbers.
When the default type is used, the maximal integer number that can be stored is 9223372036854775807 (INT64_MAX) and the minimal integer number that can be stored is -9223372036854775808 (INT64_MIN). Integer numbers that are out of range will yield over/underflow when used in a constructor. During deserialization, too large or small integer numbers will be automatically be stored as number_unsigned_t or number_float_t.
RFC 7159 further states:
Note that when such software is used, numbers that are integers and are in the range
are interoperable in the sense that implementations will agree exactly on their numeric values.
As this range is a subrange of the exactly supported range [INT64_MIN, INT64_MAX], this class's integer type is interoperable.
Storage
Integer number values are stored directly inside a basic_json type.
- See also
- number_float_t – type for number values (floating-point)
- number_unsigned_t – type for number values (unsigned integer)
- Since
- version 1.0.0
| using nlohmann::basic_json< ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType >::number_unsigned_t = NumberUnsignedType |
a type for a number (unsigned)
RFC 7159 describes numbers as follows:
The representation of numbers is similar to that used in most programming languages. A number is represented in base 10 using decimal digits. It contains an integer component that may be prefixed with an optional minus sign, which may be followed by a fraction part and/or an exponent part. Leading zeros are not allowed. (...) Numeric values that cannot be represented in the grammar below (such as Infinity and NaN) are not permitted.
This description includes both integer and floating-point numbers. However, C++ allows more precise storage if it is known whether the number is a signed integer, an unsigned integer or a floating-point number. Therefore, three different types, number_integer_t, number_unsigned_t and number_float_t are used.
To store unsigned integer numbers in C++, a type is defined by the template parameter NumberUnsignedType which chooses the type to use.
Default type
With the default values for NumberUnsignedType (uint64_t), the default value for number_unsigned_t is:
Default behavior
- The restrictions about leading zeros is not enforced in C++. Instead, leading zeros in integer literals lead to an interpretation as octal number. Internally, the value will be stored as decimal number. For instance, the C++ integer literal
010will be serialized to8. During deserialization, leading zeros yield an error. - Not-a-number (NaN) values will be serialized to
null.
Limits
RFC 7159 specifies:
An implementation may set limits on the range and precision of numbers.
When the default type is used, the maximal integer number that can be stored is 18446744073709551615 (UINT64_MAX) and the minimal integer number that can be stored is 0. Integer numbers that are out of range will yield over/underflow when used in a constructor. During deserialization, too large or small integer numbers will be automatically be stored as number_integer_t or number_float_t.
RFC 7159 further states:
Note that when such software is used, numbers that are integers and are in the range
As this range is a subrange (when considered in conjunction with the number_integer_t type) of the exactly supported range [0, UINT64_MAX], this class's integer type is interoperable.
Storage
Integer number values are stored directly inside a basic_json type.
- See also
- number_float_t – type for number values (floating-point)
- number_integer_t – type for number values (integer)
- Since
- version 2.0.0
| using nlohmann::basic_json< ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType >::object_t = ObjectType<StringType, basic_json, std::less<StringType>, AllocatorType<std::pair<const StringType, basic_json>>> |
a type for an object
RFC 7159 describes JSON objects as follows:
An object is an unordered collection of zero or more name/value pairs, where a name is a string and a value is a string, number, boolean, null, object, or array.
To store objects in C++, a type is defined by the template parameters described below.
- Template Parameters
-
ObjectType the container to store objects (e.g., std::maporstd::unordered_map)StringType the type of the keys or names (e.g., std::string). The comparison functionstd::less<StringType>is used to order elements inside the container.AllocatorType the allocator to use for objects (e.g., std::allocator)
Default type
With the default values for ObjectType (std::map), StringType (std::string), and AllocatorType (std::allocator), the default value for object_t is:
Behavior
The choice of object_t influences the behavior of the JSON class. With the default type, objects have the following behavior:
- When all names are unique, objects will be interoperable in the sense that all software implementations receiving that object will agree on the name-value mappings.
- When the names within an object are not unique, later stored name/value pairs overwrite previously stored name/value pairs, leaving the used names unique. For instance,
{"key": 1}and{"key": 2, "key": 1}will be treated as equal and both stored as{"key": 1}. - Internally, name/value pairs are stored in lexicographical order of the names. Objects will also be serialized (see dump) in this order. For instance,
{"b": 1, "a": 2}and{"a": 2, "b": 1}will be stored and serialized as{"a": 2, "b": 1}. - When comparing objects, the order of the name/value pairs is irrelevant. This makes objects interoperable in the sense that they will not be affected by these differences. For instance,
{"b": 1, "a": 2}and{"a": 2, "b": 1}will be treated as equal.
Limits
RFC 7159 specifies:
An implementation may set limits on the maximum depth of nesting.
In this class, the object's limit of nesting is not constraint explicitly. However, a maximum depth of nesting may be introduced by the compiler or runtime environment. A theoretical limit can be queried by calling the max_size function of a JSON object.
Storage
Objects are stored as pointers in a basic_json type. That is, for any access to object values, a pointer of type object_t* must be dereferenced.
- Since
- version 1.0.0
- Note
- The order name/value pairs are added to the object is not preserved by the library. Therefore, iterating an object may return name/value pairs in a different order than they were originally stored. In fact, keys will be traversed in alphabetical order as
std::mapwithstd::lessis used by default. Please note this behavior conforms to RFC 7159, because any order implements the specified "unordered" nature of JSON objects.
| using nlohmann::basic_json< ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType >::parser_callback_t = std::function<bool(int depth, parse_event_t event, basic_json& parsed)> |
per-element parser callback type
With a parser callback function, the result of parsing a JSON text can be influenced. When passed to parse(std::istream&, parser_callback_t) or parse(const string_t&, parser_callback_t), it is called on certain events (passed as parse_event_t via parameter event) with a set recursion depth depth and context JSON value parsed. The return value of the callback function is a boolean indicating whether the element that emitted the callback shall be kept or not.
We distinguish six scenarios (determined by the event type) in which the callback function can be called. The following table describes the values of the parameters depth, event, and parsed.
| parameter event | description | parameter depth | parameter parsed |
|---|---|---|---|
| parse_event_t::object_start | the parser read { and started to process a JSON object | depth of the parent of the JSON object | a JSON value with type discarded |
| parse_event_t::key | the parser read a key of a value in an object | depth of the currently parsed JSON object | a JSON string containing the key |
| parse_event_t::object_end | the parser read } and finished processing a JSON object | depth of the parent of the JSON object | the parsed JSON object |
| parse_event_t::array_start | the parser read [ and started to process a JSON array | depth of the parent of the JSON array | a JSON value with type discarded |
| parse_event_t::array_end | the parser read ] and finished processing a JSON array | depth of the parent of the JSON array | the parsed JSON array |
| parse_event_t::value | the parser finished reading a JSON value | depth of the value | the parsed JSON value |
Discarding a value (i.e., returning false) has different effects depending on the context in which function was called:
- Discarded values in structured types are skipped. That is, the parser will behave as if the discarded value was never read.
- In case a value outside a structured type is skipped, it is replaced with
null. This case happens if the top-level element is skipped.
- Parameters
-
[in] depth the depth of the recursion during parsing [in] event an event of type parse_event_t indicating the context in the callback function has been called [in,out] parsed the current intermediate parse result; note that writing to this value has no effect for parse_event_t::key events
- Returns
- Whether the JSON value which called the function during parsing should be kept (
true) or not (false). In the latter case, it is either skipped completely or replaced by an empty discarded object.
- See also
- parse(std::istream&, parser_callback_t) or parse(const string_t&, parser_callback_t) for examples
- Since
- version 1.0.0
| using nlohmann::basic_json< ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType >::string_t = StringType |
a type for a string
RFC 7159 describes JSON strings as follows:
A string is a sequence of zero or more Unicode characters.
To store objects in C++, a type is defined by the template parameter described below. Unicode values are split by the JSON class into byte-sized characters during deserialization.
- Template Parameters
-
StringType the container to store strings (e.g., std::string). Note this container is used for keys/names in objects, see object_t.
Default type
With the default values for StringType (std::string), the default value for string_t is:
String comparison
RFC 7159 states:
Software implementations are typically required to test names of object members for equality. Implementations that transform the textual representation into sequences of Unicode code units and then perform the comparison numerically, code unit by code unit, are interoperable in the sense that implementations will agree in all cases on equality or inequality of two strings. For example, implementations that compare strings with escaped characters unconverted may incorrectly find that
"a\\\\b"and"a\\u005Cb"are not equal.
This implementation is interoperable as it does compare strings code unit by code unit.
Storage
String values are stored as pointers in a basic_json type. That is, for any access to string values, a pointer of type string_t* must be dereferenced.
- Since
- version 1.0.0
Member Enumeration Documentation
|
strong |
JSON callback events.
This enumeration lists the parser events that can trigger calling a callback function of type parser_callback_t during parsing.
- Since
- version 1.0.0
|
strong |
the JSON type enumeration
This enumeration collects the different JSON types. It is internally used to distinguish the stored values, and the functions is_null(), is_object(), is_array(), is_string(), is_boolean(), is_number(), and is_discarded() rely on it.
- Since
- version 1.0.0
Constructor & Destructor Documentation
|
inline |
create an empty value with a given type
Create an empty JSON value with a given type. The value will be default initialized with an empty value which depends on the type:
| Value type | initial value |
|---|---|
| null | null |
| boolean | false |
| string | "" |
| number | 0 |
| object | {} |
| array | [] |
- Parameters
-
[in] value_type the type of the value to create
Constant.
- Exceptions
-
std::bad_alloc if allocation for object, array, or string value fails
{The following code shows the constructor for different value_t values,basic_json__value_t}
- See also
- basic_json(std::nullptr_t) – create a
nullvalue - basic_json(boolean_t value) – create a boolean value
- basic_json(const string_t&) – create a string value
- basic_json(const object_t&) – create a object value
- basic_json(const array_t&) – create a array value
- basic_json(const number_float_t) – create a number (floating-point) value
- basic_json(const number_integer_t) – create a number (integer) value
- basic_json(const number_unsigned_t) – create a number (unsigned) value
- Since
- version 1.0.0
|
default |
create a null object (implicitly)
Create a null JSON value. This is the implicit version of the null value constructor as it takes no parameters.
Constant.
No-throw guarantee: this constructor never throws exceptions.
This function helps basic_json satisfying the Container requirements:
- The complexity is constant.
- As postcondition, it holds:
basic_json().empty() == true.
{The following code shows the constructor for a null JSON value.,basic_json}
- See also
- basic_json(std::nullptr_t) – create a
nullvalue
- Since
- version 1.0.0
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|
inlinenoexcept |
create a null object (explicitly)
Create a null JSON value. This is the explicitly version of the null value constructor as it takes a null pointer as parameter. It allows to create null values by explicitly assigning a nullptr to a JSON value. The passed null pointer itself is not read – it is only used to choose the right constructor.
Constant.
No-throw guarantee: this constructor never throws exceptions.
{The following code shows the constructor with null pointer parameter.,basic_json__nullptr_t}
- See also
- basic_json() – default constructor (implicitly creating a
nullvalue)
- Since
- version 1.0.0
|
inline |
create an object (explicit)
Create an object JSON value with a given content.
- Parameters
-
[in] val a value for the object
Linear in the size of the passed val.
- Exceptions
-
std::bad_alloc if allocation for object value fails
{The following code shows the constructor with an object_t parameter.,basic_json__object_t}
- See also
- basic_json(const CompatibleObjectType&) – create an object value from a compatible STL container
- Since
- version 1.0.0
|
inline |
create an object (implicit)
Create an object JSON value with a given content. This constructor allows any type CompatibleObjectType that can be used to construct values of type object_t.
- Template Parameters
-
CompatibleObjectType An object type whose key_typeandvalue_typeis compatible to object_t. Examples includestd::map,std::unordered_map,std::multimap, andstd::unordered_multimapwith akey_typeofstd::string, and avalue_typefrom which a basic_json value can be constructed.
- Parameters
-
[in] val a value for the object
Linear in the size of the passed val.
- Exceptions
-
std::bad_alloc if allocation for object value fails
{The following code shows the constructor with several compatible object type parameters.,basic_json__CompatibleObjectType}
- See also
- basic_json(const object_t&) – create an object value
- Since
- version 1.0.0
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inline |
create an array (explicit)
Create an array JSON value with a given content.
- Parameters
-
[in] val a value for the array
Linear in the size of the passed val.
- Exceptions
-
std::bad_alloc if allocation for array value fails
{The following code shows the constructor with an array_t parameter.,basic_json__array_t}
- See also
- basic_json(const CompatibleArrayType&) – create an array value from a compatible STL containers
- Since
- version 1.0.0
|
inline |
create an array (implicit)
Create an array JSON value with a given content. This constructor allows any type CompatibleArrayType that can be used to construct values of type array_t.
- Template Parameters
-
CompatibleArrayType An object type whose value_typeis compatible to array_t. Examples includestd::vector,std::deque,std::list,std::forward_list,std::array,std::set,std::unordered_set,std::multiset, andunordered_multisetwith avalue_typefrom which a basic_json value can be constructed.
- Parameters
-
[in] val a value for the array
Linear in the size of the passed val.
- Exceptions
-
std::bad_alloc if allocation for array value fails
{The following code shows the constructor with several compatible array type parameters.,basic_json__CompatibleArrayType}
- See also
- basic_json(const array_t&) – create an array value
- Since
- version 1.0.0
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inline |
create a string (explicit)
Create an string JSON value with a given content.
- Parameters
-
[in] val a value for the string
Linear in the size of the passed val.
- Exceptions
-
std::bad_alloc if allocation for string value fails
{The following code shows the constructor with an string_t parameter.,basic_json__string_t}
- See also
- basic_json(const typename string_t::value_type*) – create a string value from a character pointer
- basic_json(const CompatibleStringType&) – create a string value from a compatible string container
- Since
- version 1.0.0
|
inline |
create a string (explicit)
Create a string JSON value with a given content.
- Parameters
-
[in] val a literal value for the string
Linear in the size of the passed val.
- Exceptions
-
std::bad_alloc if allocation for string value fails
{The following code shows the constructor with string literal parameter.,basic_json__string_t_value_type}
- See also
- basic_json(const string_t&) – create a string value
- basic_json(const CompatibleStringType&) – create a string value from a compatible string container
- Since
- version 1.0.0
|
inline |
create a string (implicit)
Create a string JSON value with a given content.
- Parameters
-
[in] val a value for the string
- Template Parameters
-
CompatibleStringType an string type which is compatible to string_t, for instance std::string.
Linear in the size of the passed val.
- Exceptions
-
std::bad_alloc if allocation for string value fails
{The following code shows the construction of a string value from a compatible type.,basic_json__CompatibleStringType}
- See also
- basic_json(const string_t&) – create a string value
- basic_json(const typename string_t::value_type*) – create a string value from a character pointer
- Since
- version 1.0.0
|
inlinenoexcept |
create a boolean (explicit)
Creates a JSON boolean type from a given value.
- Parameters
-
[in] val a boolean value to store
Constant.
{The example below demonstrates boolean values.,basic_json__boolean_t}
- Since
- version 1.0.0
|
inlinenoexcept |
create an integer number (explicit)
Create an integer number JSON value with a given content.
- Template Parameters
-
T A helper type to remove this function via SFINAE in case number_integer_t is the same as int. In this case, this constructor would have the same signature as basic_json(const int value). Note the helper type T is not visible in this constructor's interface.
- Parameters
-
[in] val an integer to create a JSON number from
Constant.
{The example below shows the construction of an integer number value.,basic_json__number_integer_t}
- See also
- basic_json(const int) – create a number value (integer)
- basic_json(const CompatibleNumberIntegerType) – create a number value (integer) from a compatible number type
- Since
- version 1.0.0
|
inlinenoexcept |
create an integer number from an enum type (explicit)
Create an integer number JSON value with a given content.
- Parameters
-
[in] val an integer to create a JSON number from
- Note
- This constructor allows to pass enums directly to a constructor. As C++ has no way of specifying the type of an anonymous enum explicitly, we can only rely on the fact that such values implicitly convert to int. As int may already be the same type of number_integer_t, we may need to switch off the constructor basic_json(const number_integer_t).
Constant.
{The example below shows the construction of an integer number value from an anonymous enum.,basic_json__const_int}
- See also
- basic_json(const number_integer_t) – create a number value (integer)
- basic_json(const CompatibleNumberIntegerType) – create a number value (integer) from a compatible number type
- Since
- version 1.0.0
|
inlinenoexcept |
create an integer number (implicit)
Create an integer number JSON value with a given content. This constructor allows any type CompatibleNumberIntegerType that can be used to construct values of type number_integer_t.
- Template Parameters
-
CompatibleNumberIntegerType An integer type which is compatible to number_integer_t. Examples include the types int,int32_t,long, andshort.
- Parameters
-
[in] val an integer to create a JSON number from
Constant.
{The example below shows the construction of several integer number values from compatible types.,basic_json__CompatibleIntegerNumberType}
- See also
- basic_json(const number_integer_t) – create a number value (integer)
- basic_json(const int) – create a number value (integer)
- Since
- version 1.0.0
|
inlinenoexcept |
create an unsigned integer number (explicit)
Create an unsigned integer number JSON value with a given content.
- Template Parameters
-
T helper type to compare number_unsigned_t and unsigned int (not visible in) the interface.
- Parameters
-
[in] val an integer to create a JSON number from
Constant.
- See also
- basic_json(const CompatibleNumberUnsignedType) – create a number value (unsigned integer) from a compatible number type
- Since
- version 2.0.0
|
inlinenoexcept |
create an unsigned number (implicit)
Create an unsigned number JSON value with a given content. This constructor allows any type CompatibleNumberUnsignedType that can be used to construct values of type number_unsigned_t.
- Template Parameters
-
CompatibleNumberUnsignedType An integer type which is compatible to number_unsigned_t. Examples may include the types unsigned int,uint32_t, orunsigned short.
- Parameters
-
[in] val an unsigned integer to create a JSON number from
Constant.
- See also
- basic_json(const number_unsigned_t) – create a number value (unsigned)
- Since
- version 2.0.0
|
inlinenoexcept |
create a floating-point number (explicit)
Create a floating-point number JSON value with a given content.
- Parameters
-
[in] val a floating-point value to create a JSON number from
- Note
- RFC 7159, section 6 disallows NaN values:
In case the parameter val is not a number, a JSON null value is created instead.Numeric values that cannot be represented in the grammar below (such as Infinity and NaN) are not permitted.
Constant.
{The following example creates several floating-point values.,basic_json__number_float_t}
- See also
- basic_json(const CompatibleNumberFloatType) – create a number value (floating-point) from a compatible number type
- Since
- version 1.0.0
|
inlinenoexcept |
create an floating-point number (implicit)
Create an floating-point number JSON value with a given content. This constructor allows any type CompatibleNumberFloatType that can be used to construct values of type number_float_t.
- Template Parameters
-
CompatibleNumberFloatType A floating-point type which is compatible to number_float_t. Examples may include the types floatordouble.
- Parameters
-
[in] val a floating-point to create a JSON number from
- Note
- RFC 7159, section 6 disallows NaN values:
In case the parameter val is not a number, a JSON null value is created instead.Numeric values that cannot be represented in the grammar below (such as Infinity and NaN) are not permitted.
Constant.
{The example below shows the construction of several floating-point number values from compatible types.,basic_json__CompatibleNumberFloatType}
- See also
- basic_json(const number_float_t) – create a number value (floating-point)
- Since
- version 1.0.0
|
inline |
create a container (array or object) from an initializer list
Creates a JSON value of type array or object from the passed initializer list init. In case type_deduction is true (default), the type of the JSON value to be created is deducted from the initializer list init according to the following rules:
- If the list is empty, an empty JSON object value
{}is created. - If the list consists of pairs whose first element is a string, a JSON object value is created where the first elements of the pairs are treated as keys and the second elements are as values.
- In all other cases, an array is created.
The rules aim to create the best fit between a C++ initializer list and JSON values. The rationale is as follows:
- The empty initializer list is written as
{}which is exactly an empty JSON object. - C++ has now way of describing mapped types other than to list a list of pairs. As JSON requires that keys must be of type string, rule 2 is the weakest constraint one can pose on initializer lists to interpret them as an object.
- In all other cases, the initializer list could not be interpreted as JSON object type, so interpreting it as JSON array type is safe.
With the rules described above, the following JSON values cannot be expressed by an initializer list:
- the empty array (
[]): use array(std::initializer_list<basic_json>) with an empty initializer list in this case - arrays whose elements satisfy rule 2: use array(std::initializer_list<basic_json>) with the same initializer list in this case
- Note
- When used without parentheses around an empty initializer list, basic_json() is called instead of this function, yielding the JSON null value.
- Parameters
-
[in] init initializer list with JSON values [in] type_deduction internal parameter; when set to true, the type of the JSON value is deducted from the initializer list init; when set tofalse, the type provided via manual_type is forced. This mode is used by the functions array(std::initializer_list<basic_json>) and object(std::initializer_list<basic_json>).[in] manual_type internal parameter; when type_deduction is set to false, the created JSON value will use the provided type (only value_t::array and value_t::object are valid); when type_deduction is set totrue, this parameter has no effect
- Exceptions
-
std::domain_error if type_deduction is false, manual_type isvalue_t::object, but init contains an element which is not a pair whose first element is a string; example:"cannot create object from initializer list"
Linear in the size of the initializer list init.
{The example below shows how JSON values are created from initializer lists.,basic_json__list_init_t}
- See also
- array(std::initializer_list<basic_json>) – create a JSON array value from an initializer list
- object(std::initializer_list<basic_json>) – create a JSON object value from an initializer list
- Since
- version 1.0.0
|
inline |
construct an array with count copies of given value
Constructs a JSON array value by creating cnt copies of a passed value. In case cnt is 0, an empty array is created. As postcondition, std::distance(begin(),end()) == cnt holds.
- Parameters
-
[in] cnt the number of JSON copies of val to create [in] val the JSON value to copy
Linear in cnt.
{The following code shows examples for the basic_json(size_type\, const basic_json&) constructor.,basic_json__size_type_basic_json}
- Since
- version 1.0.0
|
inline |
construct a JSON container given an iterator range
Constructs the JSON value with the contents of the range [first, last). The semantics depends on the different types a JSON value can have:
- In case of primitive types (number, boolean, or string), first must be
begin()and last must beend(). In this case, the value is copied. Otherwise, std::out_of_range is thrown. - In case of structured types (array, object), the constructor behaves as similar versions for
std::vector. - In case of a null type, std::domain_error is thrown.
- Template Parameters
-
InputIT an input iterator type (iterator or const_iterator)
- Parameters
-
[in] first begin of the range to copy from (included) [in] last end of the range to copy from (excluded)
- Exceptions
-
std::domain_error if iterators are not compatible; that is, do not belong to the same JSON value; example: "iterators are not compatible"std::out_of_range if iterators are for a primitive type (number, boolean, or string) where an out of range error can be detected easily; example: "iterators out of range"std::bad_alloc if allocation for object, array, or string fails std::domain_error if called with a null value; example: "cannot use construct with iterators from null"
Linear in distance between first and last.
{The example below shows several ways to create JSON values by specifying a subrange with iterators.,basic_json__InputIt_InputIt}
- Since
- version 1.0.0
|
inlineexplicit |
construct a JSON value given an input stream
- Parameters
-
[in,out] i stream to read a serialized JSON value from [in] cb a parser callback function of type parser_callback_t which is used to control the deserialization by filtering unwanted values (optional)
Linear in the length of the input. The parser is a predictive LL(1) parser. The complexity can be higher if the parser callback function cb has a super-linear complexity.
- Note
- A UTF-8 byte order mark is silently ignored.
{The example below demonstrates constructing a JSON value from a std::stringstream with and without callback function.,basic_json__istream}
- Since
- version 2.0.0
|
inline |
copy constructor
Creates a copy of a given JSON value.
- Parameters
-
[in] other the JSON value to copy
Linear in the size of other.
This function helps basic_json satisfying the Container requirements:
- The complexity is linear.
- As postcondition, it holds:
other == basic_json(other).
- Exceptions
-
std::bad_alloc if allocation for object, array, or string fails.
{The following code shows an example for the copy constructor.,basic_json__basic_json}
- Since
- version 1.0.0
|
inlinenoexcept |
move constructor
Move constructor. Constructs a JSON value with the contents of the given value other using move semantics. It "steals" the resources from other and leaves it as JSON null value.
- Parameters
-
[in,out] other value to move to this object
- Postcondition
- other is a JSON null value
Constant.
{The code below shows the move constructor explicitly called via std::move.,basic_json__moveconstructor}
- Since
- version 1.0.0
|
inline |
destructor
Destroys the JSON value and frees all allocated memory.
Linear.
This function helps basic_json satisfying the Container requirements:
- The complexity is linear.
- All stored elements are destroyed and all memory is freed.
- Since
- version 1.0.0
Member Function Documentation
|
inlinestatic |
explicitly create an array from an initializer list
Creates a JSON array value from a given initializer list. That is, given a list of values a, b, c, creates the JSON value [a, b, c]. If the initializer list is empty, the empty array [] is created.
- Note
- This function is only needed to express two edge cases that cannot be realized with the initializer list constructor (basic_json(std::initializer_list<basic_json>, bool, value_t)). These cases are:
- creating an array whose elements are all pairs whose first element is a string – in this case, the initializer list constructor would create an object, taking the first elements as keys
- creating an empty array – passing the empty initializer list to the initializer list constructor yields an empty object
- Parameters
-
[in] init initializer list with JSON values to create an array from (optional)
- Returns
- JSON array value
Linear in the size of init.
{The following code shows an example for the array function.,array}
- See also
- basic_json(std::initializer_list<basic_json>, bool, value_t) – create a JSON value from an initializer list
- object(std::initializer_list<basic_json>) – create a JSON object value from an initializer list
- Since
- version 1.0.0
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inline |
access specified array element with bounds checking
Returns a reference to the element at specified location idx, with bounds checking.
- Parameters
-
[in] idx index of the element to access
- Returns
- reference to the element at index idx
- Exceptions
-
std::domain_error if the JSON value is not an array; example: "cannot use at() with string"std::out_of_range if the index idx is out of range of the array; that is, idx >= size(); example:"array index 7 is out of range"
Constant.
{The example below shows how array elements can be read and written using at().,at__size_type}
- Since
- version 1.0.0
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inline |
access specified array element with bounds checking
Returns a const reference to the element at specified location idx, with bounds checking.
- Parameters
-
[in] idx index of the element to access
- Returns
- const reference to the element at index idx
- Exceptions
-
std::domain_error if the JSON value is not an array; example: "cannot use at() with string"std::out_of_range if the index idx is out of range of the array; that is, idx >= size(); example:"array index 7 is out of range"
Constant.
{The example below shows how array elements can be read using at().,at__size_type_const}
- Since
- version 1.0.0
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inline |
access specified object element with bounds checking
Returns a reference to the element at with specified key key, with bounds checking.
- Parameters
-
[in] key key of the element to access
- Returns
- reference to the element at key key
- Exceptions
-
std::domain_error if the JSON value is not an object; example: "cannot use at() with boolean"std::out_of_range if the key key is is not stored in the object; that is, find(key) == end(); example:"key "the fast" not found"
Logarithmic in the size of the container.
{The example below shows how object elements can be read and written using at().,at__object_t_key_type}
- See also
- operator[](const typename object_t::key_type&) for unchecked access by reference
- value() for access by value with a default value
- Since
- version 1.0.0
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inline |
access specified object element with bounds checking
Returns a const reference to the element at with specified key key, with bounds checking.
- Parameters
-
[in] key key of the element to access
- Returns
- const reference to the element at key key
- Exceptions
-
std::domain_error if the JSON value is not an object; example: "cannot use at() with boolean"std::out_of_range if the key key is is not stored in the object; that is, find(key) == end(); example:"key "the fast" not found"
Logarithmic in the size of the container.
{The example below shows how object elements can be read using at().,at__object_t_key_type_const}
- See also
- operator[](const typename object_t::key_type&) for unchecked access by reference
- value() for access by value with a default value
- Since
- version 1.0.0
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inline |
access the last element
Returns a reference to the last element in the container. For a JSON container c, the expression c.back() is equivalent to
- Returns
- In case of a structured type (array or object), a reference to the last element is returned. In cast of number, string, or boolean values, a reference to the value is returned.
Constant.
- Precondition
- The JSON value must not be
null(would throwstd::out_of_range) or an empty array or object (undefined behavior, guarded by assertions).
- Postcondition
- The JSON value remains unchanged.
- Exceptions
-
std::out_of_range when called on nullvalue.
{The following code shows an example for back().,back}
- See also
- front() – access the first element
- Since
- version 1.0.0
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inline |
access the last element
Returns a reference to the last element in the container. For a JSON container c, the expression c.back() is equivalent to
- Returns
- In case of a structured type (array or object), a reference to the last element is returned. In cast of number, string, or boolean values, a reference to the value is returned.
Constant.
- Precondition
- The JSON value must not be
null(would throwstd::out_of_range) or an empty array or object (undefined behavior, guarded by assertions).
- Postcondition
- The JSON value remains unchanged.
- Exceptions
-
std::out_of_range when called on nullvalue.
{The following code shows an example for back().,back}
- See also
- front() – access the first element
- Since
- version 1.0.0
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inlinenoexcept |
returns an iterator to the first element
Returns an iterator to the first element.
- Returns
- iterator to the first element
Constant.
This function helps basic_json satisfying the Container requirements:
- The complexity is constant.
{The following code shows an example for begin().,begin}
- See also
- cbegin() – returns a const iterator to the beginning
- end() – returns an iterator to the end
- cend() – returns a const iterator to the end
- Since
- version 1.0.0
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inlinenoexcept |
returns a const iterator to the first element
Returns a const iterator to the first element.
- Returns
- const iterator to the first element
Constant.
This function helps basic_json satisfying the Container requirements:
- The complexity is constant.
- Has the semantics of
const_cast<const basic_json&>(*this).begin().
{The following code shows an example for cbegin().,cbegin}
- See also
- begin() – returns an iterator to the beginning
- end() – returns an iterator to the end
- cend() – returns a const iterator to the end
- Since
- version 1.0.0
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inlinenoexcept |
returns a const iterator to the first element
Returns a const iterator to the first element.
- Returns
- const iterator to the first element
Constant.
This function helps basic_json satisfying the Container requirements:
- The complexity is constant.
- Has the semantics of
const_cast<const basic_json&>(*this).begin().
{The following code shows an example for cbegin().,cbegin}
- See also
- begin() – returns an iterator to the beginning
- end() – returns an iterator to the end
- cend() – returns a const iterator to the end
- Since
- version 1.0.0
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inlinenoexcept |
returns a const iterator to one past the last element
Returns a const iterator to one past the last element.
- Returns
- const iterator one past the last element
Constant.
This function helps basic_json satisfying the Container requirements:
- The complexity is constant.
- Has the semantics of
const_cast<const basic_json&>(*this).end().
{The following code shows an example for cend().,cend}
- See also
- end() – returns an iterator to the end
- begin() – returns an iterator to the beginning
- cbegin() – returns a const iterator to the beginning
- Since
- version 1.0.0
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inlinenoexcept |
clears the contents
Clears the content of a JSON value and resets it to the default value as if basic_json(value_t) would have been called:
| Value type | initial value |
|---|---|
| null | null |
| boolean | false |
| string | "" |
| number | 0 |
| object | {} |
| array | [] |
- Note
- Floating-point numbers are set to
0.0which will be serialized to0. The vale type remains number_float_t.
Linear in the size of the JSON value.
{The example below shows the effect of clear() to different JSON types.,clear}
- Since
- version 1.0.0
|
inline |
returns the number of occurrences of a key in a JSON object
Returns the number of elements with key key. If ObjectType is the default std::map type, the return value will always be 0 (key was not found) or 1 (key was found).
- Parameters
-
[in] key key value of the element to count
- Returns
- Number of elements with key key. If the JSON value is not an object, the return value will be
0.
Logarithmic in the size of the JSON object.
{The example shows how count() is used.,count}
- Since
- version 1.0.0
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inlinenoexcept |
returns a const reverse iterator to the last element
Returns a const iterator to the reverse-beginning; that is, the last element.
Constant.
This function helps basic_json satisfying the ReversibleContainer requirements:
- The complexity is constant.
- Has the semantics of
const_cast<const basic_json&>(*this).rbegin().
{The following code shows an example for crbegin().,crbegin}
- See also
- rbegin() – returns a reverse iterator to the beginning
- rend() – returns a reverse iterator to the end
- crend() – returns a const reverse iterator to the end
- Since
- version 1.0.0
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inlinenoexcept |
returns a const reverse iterator to one before the first
Returns a const reverse iterator to the reverse-end; that is, one before the first element.
Constant.
This function helps basic_json satisfying the ReversibleContainer requirements:
- The complexity is constant.
- Has the semantics of
const_cast<const basic_json&>(*this).rend().
{The following code shows an example for crend().,crend}
- See also
- rend() – returns a reverse iterator to the end
- rbegin() – returns a reverse iterator to the beginning
- crbegin() – returns a const reverse iterator to the beginning
- Since
- version 1.0.0
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inline |
serialization
Serialization function for JSON values. The function tries to mimic Python's json.dumps() function, and currently supports its indent parameter.
- Parameters
-
[in] indent if indent is nonnegative, then array elements and object members will be pretty-printed with that indent level. An indent level of 0 will only insert newlines. -1 (the default) selects the most compact representation
- Returns
- string containing the serialization of the JSON value
Linear.
{The following example shows the effect of different indent parameters to the result of the serialization.,dump}
- Since
- version 1.0.0
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inlinenoexcept |
checks whether the container is empty
Checks if a JSON value has no elements.
- Returns
- The return value depends on the different types and is defined as follows:
Constant, as long as array_t and object_t satisfy the Container concept; that is, theirValue type return value null trueboolean falsestring falsenumber falseobject result of function object_t::empty()array result of function array_t::empty()empty()functions have constant complexity.
This function helps basic_json satisfying the Container requirements:
{The following code uses empty() to check if a JSON object contains any elements.,empty}
- See also
- size() – returns the number of elements
- Since
- version 1.0.0
|
inlinenoexcept |
returns an iterator to one past the last element
Returns an iterator to one past the last element.
- Returns
- iterator one past the last element
Constant.
This function helps basic_json satisfying the Container requirements:
- The complexity is constant.
{The following code shows an example for end().,end}
- See also
- cend() – returns a const iterator to the end
- begin() – returns an iterator to the beginning
- cbegin() – returns a const iterator to the beginning
- Since
- version 1.0.0
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inlinenoexcept |
returns a const iterator to one past the last element
Returns a const iterator to one past the last element.
- Returns
- const iterator one past the last element
Constant.
This function helps basic_json satisfying the Container requirements:
- The complexity is constant.
- Has the semantics of
const_cast<const basic_json&>(*this).end().
{The following code shows an example for cend().,cend}
- See also
- end() – returns an iterator to the end
- begin() – returns an iterator to the beginning
- cbegin() – returns a const iterator to the beginning
- Since
- version 1.0.0
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inline |
remove element given an iterator
Removes the element specified by iterator pos. The iterator pos must be valid and dereferenceable. Thus the end() iterator (which is valid, but is not dereferenceable) cannot be used as a value for pos.
If called on a primitive type other than null, the resulting JSON value will be null.
- Parameters
-
[in] pos iterator to the element to remove
- Returns
- Iterator following the last removed element. If the iterator pos refers to the last element, the
end()iterator is returned.
- Template Parameters
-
InteratorType an iterator or const_iterator
- Postcondition
- Invalidates iterators and references at or after the point of the erase, including the
end()iterator.
- Exceptions
-
std::domain_error if called on a nullvalue; example:"cannot use erase() with null"std::domain_error if called on an iterator which does not belong to the current JSON value; example: "iterator does not fit current value"std::out_of_range if called on a primitive type with invalid iterator (i.e., any iterator which is not begin()); example:"iterator out of range"
The complexity depends on the type:
- objects: amortized constant
- arrays: linear in distance between pos and the end of the container
- strings: linear in the length of the string
- other types: constant
{The example shows the result of erase() for different JSON types.,erase__IteratorType}
- See also
- erase(InteratorType, InteratorType) – removes the elements in the given range
- erase(const typename object_t::key_type&) – removes the element from an object at the given key
- erase(const size_type) – removes the element from an array at the given index
- Since
- version 1.0.0
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inline |
remove elements given an iterator range
Removes the element specified by the range [first; last). The iterator first does not need to be dereferenceable if first == last: erasing an empty range is a no-op.
If called on a primitive type other than null, the resulting JSON value will be null.
- Parameters
-
[in] first iterator to the beginning of the range to remove [in] last iterator past the end of the range to remove
- Returns
- Iterator following the last removed element. If the iterator second refers to the last element, the
end()iterator is returned.
- Template Parameters
-
InteratorType an iterator or const_iterator
- Postcondition
- Invalidates iterators and references at or after the point of the erase, including the
end()iterator.
- Exceptions
-
std::domain_error if called on a nullvalue; example:"cannot use erase() with null"std::domain_error if called on iterators which does not belong to the current JSON value; example: "iterators do not fit current value"std::out_of_range if called on a primitive type with invalid iterators (i.e., if first != begin()andlast != end()); example:"iterators out of range"
The complexity depends on the type:
- objects:
log(size()) + std::distance(first, last) - arrays: linear in the distance between first and last, plus linear in the distance between last and end of the container
- strings: linear in the length of the string
- other types: constant
{The example shows the result of erase() for different JSON types.,erase__IteratorType_IteratorType}
- See also
- erase(InteratorType) – removes the element at a given position
- erase(const typename object_t::key_type&) – removes the element from an object at the given key
- erase(const size_type) – removes the element from an array at the given index
- Since
- version 1.0.0
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remove element from a JSON object given a key
Removes elements from a JSON object with the key value key.
- Parameters
-
[in] key value of the elements to remove
- Returns
- Number of elements removed. If ObjectType is the default
std::maptype, the return value will always be0(key was not found) or1(key was found).
- Postcondition
- References and iterators to the erased elements are invalidated. Other references and iterators are not affected.
- Exceptions
-
std::domain_error when called on a type other than JSON object; example: "cannot use erase() with null"
log(size()) + count(key)
{The example shows the effect of erase().,erase__key_type}
- See also
- erase(InteratorType) – removes the element at a given position
- erase(InteratorType, InteratorType) – removes the elements in the given range
- erase(const size_type) – removes the element from an array at the given index
- Since
- version 1.0.0
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inline |
remove element from a JSON array given an index
Removes element from a JSON array at the index idx.
- Parameters
-
[in] idx index of the element to remove
- Exceptions
-
std::domain_error when called on a type other than JSON array; example: "cannot use erase() with null"std::out_of_range when idx >= size(); example:"index out of range"
Linear in distance between idx and the end of the container.
{The example shows the effect of erase().,erase__size_type}
- See also
- erase(InteratorType) – removes the element at a given position
- erase(InteratorType, InteratorType) – removes the elements in the given range
- erase(const typename object_t::key_type&) – removes the element from an object at the given key
- Since
- version 1.0.0
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inline |
find an element in a JSON object
Finds an element in a JSON object with key equivalent to key. If the element is not found or the JSON value is not an object, end() is returned.
- Parameters
-
[in] key key value of the element to search for
- Returns
- Iterator to an element with key equivalent to key. If no such element is found, past-the-end (see end()) iterator is returned.
Logarithmic in the size of the JSON object.
{The example shows how find() is used.,find__key_type}
- Since
- version 1.0.0
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inline |
find an element in a JSON object
find an element in a JSON object Finds an element in a JSON object with key equivalent to key. If the element is not found or the JSON value is not an object, end() is returned.
- Parameters
-
[in] key key value of the element to search for
- Returns
- Iterator to an element with key equivalent to key. If no such element is found, past-the-end (see end()) iterator is returned.
Logarithmic in the size of the JSON object.
{The example shows how find() is used.,find__key_type}
- Since
- version 1.0.0
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inline |
access the first element
Returns a reference to the first element in the container. For a JSON container c, the expression c.front() is equivalent to *c.begin().
- Returns
- In case of a structured type (array or object), a reference to the first element is returned. In cast of number, string, or boolean values, a reference to the value is returned.
Constant.
- Precondition
- The JSON value must not be
null(would throwstd::out_of_range) or an empty array or object (undefined behavior, guarded by assertions).
- Postcondition
- The JSON value remains unchanged.
- Exceptions
-
std::out_of_range when called on nullvalue
{The following code shows an example for front().,front}
- See also
- back() – access the last element
- Since
- version 1.0.0
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inline |
access the first element
Returns a reference to the first element in the container. For a JSON container c, the expression c.front() is equivalent to *c.begin().
- Returns
- In case of a structured type (array or object), a reference to the first element is returned. In cast of number, string, or boolean values, a reference to the value is returned.
Constant.
- Precondition
- The JSON value must not be
null(would throwstd::out_of_range) or an empty array or object (undefined behavior, guarded by assertions).
- Postcondition
- The JSON value remains unchanged.
- Exceptions
-
std::out_of_range when called on nullvalue
{The following code shows an example for front().,front}
- See also
- back() – access the last element
- Since
- version 1.0.0
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get a value (explicit)
Explicit type conversion between the JSON value and a compatible value.
- Template Parameters
-
ValueType non-pointer type compatible to the JSON value, for instance intfor JSON integer numbers,boolfor JSON booleans, orstd::vectortypes for JSON arrays
- Returns
- copy of the JSON value, converted to type ValueType
- Exceptions
-
std::domain_error in case passed type ValueType is incompatible to JSON; example: "type must be object, but is null"
Linear in the size of the JSON value.
{The example below shows several conversions from JSON values to other types. There a few things to note: (1) Floating-point numbers can be converted to integers\, (2) A JSON array can be converted to a standard std::vector<short>\, (3) A JSON object can be converted to C++ associative containers such as std::unordered_map<std::string\, json>.,get__ValueType_const}
- See also
- operator ValueType() const for implicit conversion
- get() for pointer-member access
- Since
- version 1.0.0
|
inlinenoexcept |
get a pointer value (explicit)
Explicit pointer access to the internally stored JSON value. No copies are made.
- Warning
- The pointer becomes invalid if the underlying JSON object changes.
- Template Parameters
-
PointerType pointer type; must be a pointer to array_t, object_t, string_t, boolean_t, number_integer_t, number_unsigned_t, or number_float_t.
- Returns
- pointer to the internally stored JSON value if the requested pointer type PointerType fits to the JSON value;
nullptrotherwise
Constant.
{The example below shows how pointers to internal values of a JSON value can be requested. Note that no type conversions are made and a nullptr is returned if the value and the requested pointer type does not match.,get__PointerType}
- See also
- get_ptr() for explicit pointer-member access
- Since
- version 1.0.0
|
inlinenoexcept |
get a pointer value (explicit)
get a pointer value (explicit) Explicit pointer access to the internally stored JSON value. No copies are made.
- Warning
- The pointer becomes invalid if the underlying JSON object changes.
- Template Parameters
-
PointerType pointer type; must be a pointer to array_t, object_t, string_t, boolean_t, number_integer_t, number_unsigned_t, or number_float_t.
- Returns
- pointer to the internally stored JSON value if the requested pointer type PointerType fits to the JSON value;
nullptrotherwise
Constant.
{The example below shows how pointers to internal values of a JSON value can be requested. Note that no type conversions are made and a nullptr is returned if the value and the requested pointer type does not match.,get__PointerType}
- See also
- get_ptr() for explicit pointer-member access
- Since
- version 1.0.0
|
inlinenoexcept |
get a pointer value (implicit)
Implicit pointer access to the internally stored JSON value. No copies are made.
- Warning
- Writing data to the pointee of the result yields an undefined state.
- Template Parameters
-
PointerType pointer type; must be a pointer to array_t, object_t, string_t, boolean_t, number_integer_t, number_unsigned_t, or number_float_t.
- Returns
- pointer to the internally stored JSON value if the requested pointer type PointerType fits to the JSON value;
nullptrotherwise
Constant.
{The example below shows how pointers to internal values of a JSON value can be requested. Note that no type conversions are made and a nullptr is returned if the value and the requested pointer type does not match.,get_ptr}
- Since
- version 1.0.0
|
inlinenoexcept |
get a pointer value (implicit)
get a pointer value (implicit) Implicit pointer access to the internally stored JSON value. No copies are made.
- Warning
- Writing data to the pointee of the result yields an undefined state.
- Template Parameters
-
PointerType pointer type; must be a pointer to array_t, object_t, string_t, boolean_t, number_integer_t, number_unsigned_t, or number_float_t.
- Returns
- pointer to the internally stored JSON value if the requested pointer type PointerType fits to the JSON value;
nullptrotherwise
Constant.
{The example below shows how pointers to internal values of a JSON value can be requested. Note that no type conversions are made and a nullptr is returned if the value and the requested pointer type does not match.,get_ptr}
- Since
- version 1.0.0
|
inline |
get a reference value (implicit)
Implict reference access to the internally stored JSON value. No copies are made.
- Warning
- Writing data to the referee of the result yields an undefined state.
- Template Parameters
-
ReferenceType reference type; must be a reference to array_t, object_t, string_t, boolean_t, number_integer_t, or number_float_t.
- Returns
- reference to the internally stored JSON value if the requested reference type ReferenceType fits to the JSON value; throws std::domain_error otherwise
- Exceptions
-
std::domain_error in case passed type ReferenceType is incompatible with the stored JSON value
Constant.
{The example shows several calls to get_ref().,get_ref}
- Since
- version 1.1.0
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inline |
get a reference value (implicit)
get a reference value (implicit) Implict reference access to the internally stored JSON value. No copies are made.
- Warning
- Writing data to the referee of the result yields an undefined state.
- Template Parameters
-
ReferenceType reference type; must be a reference to array_t, object_t, string_t, boolean_t, number_integer_t, or number_float_t.
- Returns
- reference to the internally stored JSON value if the requested reference type ReferenceType fits to the JSON value; throws std::domain_error otherwise
- Exceptions
-
std::domain_error in case passed type ReferenceType is incompatible with the stored JSON value
Constant.
{The example shows several calls to get_ref().,get_ref}
- Since
- version 1.1.0
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inline |
inserts element
Inserts element val before iterator pos.
- Parameters
-
[in] pos iterator before which the content will be inserted; may be the end() iterator [in] val element to insert
- Returns
- iterator pointing to the inserted val.
- Exceptions
-
std::domain_error if called on JSON values other than arrays; example: "cannot use insert() with string"std::domain_error if pos is not an iterator of *this; example: "iterator does not fit current value"
Constant plus linear in the distance between pos and end of the container.
{The example shows how insert() is used.,insert}
- Since
- version 1.0.0
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inline |
inserts element
inserts element Inserts element val before iterator pos.
- Parameters
-
[in] pos iterator before which the content will be inserted; may be the end() iterator [in] val element to insert
- Returns
- iterator pointing to the inserted val.
- Exceptions
-
std::domain_error if called on JSON values other than arrays; example: "cannot use insert() with string"std::domain_error if pos is not an iterator of *this; example: "iterator does not fit current value"
Constant plus linear in the distance between pos and end of the container.
{The example shows how insert() is used.,insert}
- Since
- version 1.0.0
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inline |
inserts elements
Inserts cnt copies of val before iterator pos.
- Parameters
-
[in] pos iterator before which the content will be inserted; may be the end() iterator [in] cnt number of copies of val to insert [in] val element to insert
- Returns
- iterator pointing to the first element inserted, or pos if
cnt==0
- Exceptions
-
std::domain_error if called on JSON values other than arrays; example: "cannot use insert() with string"std::domain_error if pos is not an iterator of *this; example: "iterator does not fit current value"
Linear in cnt plus linear in the distance between pos and end of the container.
{The example shows how insert() is used.,insert__count}
- Since
- version 1.0.0
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inserts elements
Inserts elements from range [first, last) before iterator pos.
- Parameters
-
[in] pos iterator before which the content will be inserted; may be the end() iterator [in] first begin of the range of elements to insert [in] last end of the range of elements to insert
- Exceptions
-
std::domain_error if called on JSON values other than arrays; example: "cannot use insert() with string"std::domain_error if pos is not an iterator of *this; example: "iterator does not fit current value"std::domain_error if first and last do not belong to the same JSON value; example: "iterators do not fit"std::domain_error if first or last are iterators into container for which insert is called; example: "passed iterators may not belong to container"
- Returns
- iterator pointing to the first element inserted, or pos if
first==last
Linear in std::distance(first, last) plus linear in the distance between pos and end of the container.
{The example shows how insert() is used.,insert__range}
- Since
- version 1.0.0
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inline |
inserts elements
Inserts elements from initializer list ilist before iterator pos.
- Parameters
-
[in] pos iterator before which the content will be inserted; may be the end() iterator [in] ilist initializer list to insert the values from
- Exceptions
-
std::domain_error if called on JSON values other than arrays; example: "cannot use insert() with string"std::domain_error if pos is not an iterator of *this; example: "iterator does not fit current value"
- Returns
- iterator pointing to the first element inserted, or pos if
ilistis empty
Linear in ilist.size() plus linear in the distance between pos and end of the container.
{The example shows how insert() is used.,insert__ilist}
- Since
- version 1.0.0
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inlinenoexcept |
return whether value is an array
This function returns true iff the JSON value is an array.
- Returns
trueif type is array,falseotherwise.
Constant.
No-throw guarantee: this member function never throws exceptions.
{The following code exemplifies is_array() for all JSON types.,is_array}
- Since
- version 1.0.0
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inlinenoexcept |
return whether value is a boolean
This function returns true iff the JSON value is a boolean.
- Returns
trueif type is boolean,falseotherwise.
Constant.
No-throw guarantee: this member function never throws exceptions.
{The following code exemplifies is_boolean() for all JSON types.,is_boolean}
- Since
- version 1.0.0
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inlinenoexcept |
return whether value is discarded
This function returns true iff the JSON value was discarded during parsing with a callback function (see parser_callback_t).
- Note
- This function will always be
falsefor JSON values after parsing. That is, discarded values can only occur during parsing, but will be removed when inside a structured value or replaced by null in other cases.
- Returns
trueif type is discarded,falseotherwise.
Constant.
No-throw guarantee: this member function never throws exceptions.
{The following code exemplifies is_discarded() for all JSON types.,is_discarded}
- Since
- version 1.0.0
|
inlinenoexcept |
return whether value is null
This function returns true iff the JSON value is null.
- Returns
trueif type is null,falseotherwise.
Constant.
No-throw guarantee: this member function never throws exceptions.
{The following code exemplifies is_null() for all JSON types.,is_null}
- Since
- version 1.0.0
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inlinenoexcept |
return whether value is a number
This function returns true iff the JSON value is a number. This includes both integer and floating-point values.
- Returns
trueif type is number (regardless whether integer, unsigned integer or floating-type),falseotherwise.
Constant.
No-throw guarantee: this member function never throws exceptions.
{The following code exemplifies is_number() for all JSON types.,is_number}
- See also
- is_number_integer() – check if value is an integer or unsigned integer number
- is_number_unsigned() – check if value is an unsigned integer number
- is_number_float() – check if value is a floating-point number
- Since
- version 1.0.0
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inlinenoexcept |
return whether value is a floating-point number
This function returns true iff the JSON value is a floating-point number. This excludes integer and unsigned integer values.
- Returns
trueif type is a floating-point number,falseotherwise.
Constant.
No-throw guarantee: this member function never throws exceptions.
{The following code exemplifies is_number_float() for all JSON types.,is_number_float}
- See also
- is_number() – check if value is number
- is_number_integer() – check if value is an integer number
- is_number_unsigned() – check if value is an unsigned integer number
- Since
- version 1.0.0
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inlinenoexcept |
return whether value is an integer number
This function returns true iff the JSON value is an integer or unsigned integer number. This excludes floating-point values.
- Returns
trueif type is an integer or unsigned integer number,falseotherwise.
Constant.
No-throw guarantee: this member function never throws exceptions.
{The following code exemplifies is_number_integer() for all JSON types.,is_number_integer}
- See also
- is_number() – check if value is a number
- is_number_unsigned() – check if value is an unsigned integer number
- is_number_float() – check if value is a floating-point number
- Since
- version 1.0.0
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return whether value is an unsigned integer number
This function returns true iff the JSON value is an unsigned integer number. This excludes floating-point and (signed) integer values.
- Returns
trueif type is an unsigned integer number,falseotherwise.
Constant.
No-throw guarantee: this member function never throws exceptions.
{The following code exemplifies is_number_unsigned() for all JSON types.,is_number_unsigned}
- See also
- is_number() – check if value is a number
- is_number_integer() – check if value is an integer or unsigned integer number
- is_number_float() – check if value is a floating-point number
- Since
- version 2.0.0
|
inlinenoexcept |
return whether value is an object
This function returns true iff the JSON value is an object.
- Returns
trueif type is object,falseotherwise.
Constant.
No-throw guarantee: this member function never throws exceptions.
{The following code exemplifies is_object() for all JSON types.,is_object}
- Since
- version 1.0.0
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return whether type is primitive
This function returns true iff the JSON type is primitive (string, number, boolean, or null).
- Returns
trueif type is primitive (string, number, boolean, or null),falseotherwise.
Constant.
No-throw guarantee: this member function never throws exceptions.
{The following code exemplifies is_primitive() for all JSON types.,is_primitive}
- See also
- is_structured() – returns whether JSON value is structured
-
is_null() – returns whether JSON value is
null - is_string() – returns whether JSON value is a string
- is_boolean() – returns whether JSON value is a boolean
- is_number() – returns whether JSON value is a number
- Since
- version 1.0.0
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inlinenoexcept |
return whether value is a string
This function returns true iff the JSON value is a string.
- Returns
trueif type is string,falseotherwise.
Constant.
No-throw guarantee: this member function never throws exceptions.
{The following code exemplifies is_string() for all JSON types.,is_string}
- Since
- version 1.0.0
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return whether type is structured
This function returns true iff the JSON type is structured (array or object).
- Returns
trueif type is structured (array or object),falseotherwise.
Constant.
No-throw guarantee: this member function never throws exceptions.
{The following code exemplifies is_structured() for all JSON types.,is_structured}
- See also
- is_primitive() – returns whether value is primitive
- is_array() – returns whether value is an array
- is_object() – returns whether value is an object
- Since
- version 1.0.0
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inlinestatic |
wrapper to access iterator member functions in range-based for
This function allows to access iterator::key() and iterator::value() during range-based for loops. In these loops, a reference to the JSON values is returned, so there is no access to the underlying iterator.
- Note
- The name of this function is not yet final and may change in the future.
|
inlinestatic |
wrapper to access iterator member functions in range-based for
This function allows to access iterator::key() and iterator::value() during range-based for loops. In these loops, a reference to the JSON values is returned, so there is no access to the underlying iterator.
- Note
- The name of this function is not yet final and may change in the future.
|
inlinenoexcept |
returns the maximum possible number of elements
Returns the maximum number of elements a JSON value is able to hold due to system or library implementation limitations, i.e. std::distance(begin(), end()) for the JSON value.
- Returns
- The return value depends on the different types and is defined as follows:
Constant, as long as array_t and object_t satisfy the Container concept; that is, theirValue type return value null 0(same assize())boolean 1(same assize())string 1(same assize())number 1(same assize())object result of function object_t::max_size()array result of function array_t::max_size()max_size()functions have constant complexity.
This function helps basic_json satisfying the Container requirements:
- The complexity is constant.
- Has the semantics of returning
b.size()wherebis the largest possible JSON value.
{The following code calls max_size() on the different value types. Note the output is implementation specific.,max_size}
- See also
- size() – returns the number of elements
- Since
- version 1.0.0
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inlinestatic |
explicitly create an object from an initializer list
Creates a JSON object value from a given initializer list. The initializer lists elements must be pairs, and their first elements must be strings. If the initializer list is empty, the empty object {} is created.
- Note
- This function is only added for symmetry reasons. In contrast to the related function array(std::initializer_list<basic_json>), there are no cases which can only be expressed by this function. That is, any initializer list init can also be passed to the initializer list constructor basic_json(std::initializer_list<basic_json>, bool, value_t).
- Parameters
-
[in] init initializer list to create an object from (optional)
- Returns
- JSON object value
- Exceptions
-
std::domain_error if init is not a pair whose first elements are strings; thrown by basic_json(std::initializer_list<basic_json>, bool, value_t)
Linear in the size of init.
{The following code shows an example for the object function.,object}
- See also
- basic_json(std::initializer_list<basic_json>, bool, value_t) – create a JSON value from an initializer list
- array(std::initializer_list<basic_json>) – create a JSON array value from an initializer list
- Since
- version 1.0.0
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return the type of the JSON value (implicit)
Implicitly return the type of the JSON value as a value from the value_t enumeration.
- Returns
- the type of the JSON value
Constant.
No-throw guarantee: this member function never throws exceptions.
{The following code exemplifies the value_t operator for all JSON types.,operator__value_t}
- Since
- version 1.0.0
|
inline |
get a value (implicit)
Implicit type conversion between the JSON value and a compatible value. The call is realized by calling get() const.
- Template Parameters
-
ValueType non-pointer type compatible to the JSON value, for instance intfor JSON integer numbers,boolfor JSON booleans, orstd::vectortypes for JSON arrays. The character type of string_t as well as an initializer list of this type is excluded to avoid ambiguities as these types implicitly convert tostd::string.
- Returns
- copy of the JSON value, converted to type ValueType
- Exceptions
-
std::domain_error in case passed type ValueType is incompatible to JSON, thrown by get() const
Linear in the size of the JSON value.
{The example below shows several conversions from JSON values to other types. There a few things to note: (1) Floating-point numbers can be converted to integers\, (2) A JSON array can be converted to a standard std::vector<short>\, (3) A JSON object can be converted to C++ associative containers such as std::unordered_map<std::string\, json>.,operator__ValueType}
- Since
- version 1.0.0
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inline |
add an object to an array
add an object to an array Appends the given element val to the end of the JSON value. If the function is called on a JSON null value, an empty array is created before appending val.
- Parameters
-
[in] val the value to add to the JSON array
- Exceptions
-
std::domain_error when called on a type other than JSON array or null; example: "cannot use push_back() with number"
Amortized constant.
{The example shows how push_back() and += can be used to add elements to a JSON array. Note how the null value was silently converted to a JSON array.,push_back}
- Since
- version 1.0.0
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inline |
add an object to an array
add an object to an array Appends the given element val to the end of the JSON value. If the function is called on a JSON null value, an empty array is created before appending val.
- Parameters
-
[in] val the value to add to the JSON array
- Exceptions
-
std::domain_error when called on a type other than JSON array or null; example: "cannot use push_back() with number"
Amortized constant.
{The example shows how push_back() and += can be used to add elements to a JSON array. Note how the null value was silently converted to a JSON array.,push_back}
- Since
- version 1.0.0
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add an object to an object
add an object to an object Inserts the given element val to the JSON object. If the function is called on a JSON null value, an empty object is created before inserting val.
- Parameters
-
[in] val the value to add to the JSON object
- Exceptions
-
std::domain_error when called on a type other than JSON object or null; example: "cannot use push_back() with number"
Logarithmic in the size of the container, O(log(size())).
{The example shows how push_back() and += can be used to add elements to a JSON object. Note how the null value was silently converted to a JSON object.,push_back__object_t__value}
- Since
- version 1.0.0
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inlinenoexcept |
copy assignment
Copy assignment operator. Copies a JSON value via the "copy and swap" strategy: It is expressed in terms of the copy constructor, destructor, and the swap() member function.
- Parameters
-
[in] other value to copy from
Linear.
This function helps basic_json satisfying the Container requirements:
- The complexity is linear.
{The code below shows and example for the copy assignment. It creates a copy of value a which is then swapped with b. Finally\, the copy of a (which is the null value after the swap) is destroyed.,basic_json__copyassignment}
- Since
- version 1.0.0
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access specified array element
Returns a reference to the element at specified location idx.
- Note
- If idx is beyond the range of the array (i.e.,
idx >= size()), then the array is silently filled up withnullvalues to makeidxa valid reference to the last stored element.
- Parameters
-
[in] idx index of the element to access
- Returns
- reference to the element at index idx
- Exceptions
-
std::domain_error if JSON is not an array or null; example: "cannot use operator[] with string"
Constant if idx is in the range of the array. Otherwise linear in idx - size().
{The example below shows how array elements can be read and written using [] operator. Note the addition of null values.,operatorarray__size_type}
- Since
- version 1.0.0
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access specified array element
Returns a const reference to the element at specified location idx.
- Parameters
-
[in] idx index of the element to access
- Returns
- const reference to the element at index idx
- Exceptions
-
std::domain_error if JSON is not an array; example: "cannot use operator[] with null"
Constant.
{The example below shows how array elements can be read using the [] operator.,operatorarray__size_type_const}
- Since
- version 1.0.0
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access specified object element
Returns a reference to the element at with specified key key.
- Note
- If key is not found in the object, then it is silently added to the object and filled with a
nullvalue to makekeya valid reference. In case the value wasnullbefore, it is converted to an object.
- Parameters
-
[in] key key of the element to access
- Returns
- reference to the element at key key
- Exceptions
-
std::domain_error if JSON is not an object or null; example: "cannot use operator[] with string"
Logarithmic in the size of the container.
{The example below shows how object elements can be read and written using the [] operator.,operatorarray__key_type}
- See also
- at(const typename object_t::key_type&) for access by reference with range checking
- value() for access by value with a default value
- Since
- version 1.0.0
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read-only access specified object element
Returns a const reference to the element at with specified key key. No bounds checking is performed.
- Warning
- If the element with key key does not exist, the behavior is undefined.
- Parameters
-
[in] key key of the element to access
- Returns
- const reference to the element at key key
- Exceptions
-
std::domain_error if JSON is not an object; example: "cannot use operator[] with null"
Logarithmic in the size of the container.
{The example below shows how object elements can be read using the [] operator.,operatorarray__key_type_const}
- See also
- at(const typename object_t::key_type&) for access by reference with range checking
- value() for access by value with a default value
- Since
- version 1.0.0
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access specified object element
Returns a reference to the element at with specified key key.
- Note
- If key is not found in the object, then it is silently added to the object and filled with a
nullvalue to makekeya valid reference. In case the value wasnullbefore, it is converted to an object.
- Parameters
-
[in] key key of the element to access
- Returns
- reference to the element at key key
- Exceptions
-
std::domain_error if JSON is not an object or null; example: "cannot use operator[] with string"
Logarithmic in the size of the container.
{The example below shows how object elements can be read and written using the [] operator.,operatorarray__key_type}
- See also
- at(const typename object_t::key_type&) for access by reference with range checking
- value() for access by value with a default value
- Since
- version 1.0.0
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read-only access specified object element
Returns a const reference to the element at with specified key key. No bounds checking is performed.
- Warning
- If the element with key key does not exist, the behavior is undefined.
- Note
- This function is required for compatibility reasons with Clang.
- Parameters
-
[in] key key of the element to access
- Returns
- const reference to the element at key key
- Exceptions
-
std::domain_error if JSON is not an object; example: "cannot use operator[] with null"
Logarithmic in the size of the container.
{The example below shows how object elements can be read using the [] operator.,operatorarray__key_type_const}
- See also
- at(const typename object_t::key_type&) for access by reference with range checking
- value() for access by value with a default value
- Since
- version 1.0.0
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access specified object element
Returns a reference to the element at with specified key key.
- Note
- If key is not found in the object, then it is silently added to the object and filled with a
nullvalue to makekeya valid reference. In case the value wasnullbefore, it is converted to an object.
- Parameters
-
[in] key key of the element to access
- Returns
- reference to the element at key key
- Exceptions
-
std::domain_error if JSON is not an object or null; example: "cannot use operator[] with string"
Logarithmic in the size of the container.
{The example below shows how object elements can be read and written using the [] operator.,operatorarray__key_type}
- See also
- at(const typename object_t::key_type&) for access by reference with range checking
- value() for access by value with a default value
- Since
- version 1.1.0
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read-only access specified object element
Returns a const reference to the element at with specified key key. No bounds checking is performed.
- Warning
- If the element with key key does not exist, the behavior is undefined.
- Parameters
-
[in] key key of the element to access
- Returns
- const reference to the element at key key
- Exceptions
-
std::domain_error if JSON is not an object; example: "cannot use operator[] with null"
Logarithmic in the size of the container.
{The example below shows how object elements can be read using the [] operator.,operatorarray__key_type_const}
- See also
- at(const typename object_t::key_type&) for access by reference with range checking
- value() for access by value with a default value
- Since
- version 1.1.0
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inlinestatic |
deserialize from string
- Parameters
-
[in] s string to read a serialized JSON value from [in] cb a parser callback function of type parser_callback_t which is used to control the deserialization by filtering unwanted values (optional)
- Returns
- result of the deserialization
Linear in the length of the input. The parser is a predictive LL(1) parser. The complexity can be higher if the parser callback function cb has a super-linear complexity.
- Note
- A UTF-8 byte order mark is silently ignored.
{The example below demonstrates the parse() function with and without callback function.,parse__string__parser_callback_t}
- See also
- parse(std::istream&, parser_callback_t) for a version that reads from an input stream
- Since
- version 1.0.0
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inlinestatic |
deserialize from stream
- Parameters
-
[in,out] i stream to read a serialized JSON value from [in] cb a parser callback function of type parser_callback_t which is used to control the deserialization by filtering unwanted values (optional)
- Returns
- result of the deserialization
Linear in the length of the input. The parser is a predictive LL(1) parser. The complexity can be higher if the parser callback function cb has a super-linear complexity.
- Note
- A UTF-8 byte order mark is silently ignored.
{The example below demonstrates the parse() function with and without callback function.,parse__istream__parser_callback_t}
- See also
- parse(const string_t&, parser_callback_t) for a version that reads from a string
- Since
- version 1.0.0
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inlinestatic |
deserialize from stream
- Parameters
-
[in,out] i stream to read a serialized JSON value from [in] cb a parser callback function of type parser_callback_t which is used to control the deserialization by filtering unwanted values (optional)
- Returns
- result of the deserialization
Linear in the length of the input. The parser is a predictive LL(1) parser. The complexity can be higher if the parser callback function cb has a super-linear complexity.
- Note
- A UTF-8 byte order mark is silently ignored.
{The example below demonstrates the parse() function with and without callback function.,parse__istream__parser_callback_t}
- See also
- parse(const string_t&, parser_callback_t) for a version that reads from a string
- Since
- version 1.0.0
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add an object to an array
Appends the given element val to the end of the JSON value. If the function is called on a JSON null value, an empty array is created before appending val.
- Parameters
-
[in] val the value to add to the JSON array
- Exceptions
-
std::domain_error when called on a type other than JSON array or null; example: "cannot use push_back() with number"
Amortized constant.
{The example shows how push_back() and += can be used to add elements to a JSON array. Note how the null value was silently converted to a JSON array.,push_back}
- Since
- version 1.0.0
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add an object to an array
add an object to an array Appends the given element val to the end of the JSON value. If the function is called on a JSON null value, an empty array is created before appending val.
- Parameters
-
[in] val the value to add to the JSON array
- Exceptions
-
std::domain_error when called on a type other than JSON array or null; example: "cannot use push_back() with number"
Amortized constant.
{The example shows how push_back() and += can be used to add elements to a JSON array. Note how the null value was silently converted to a JSON array.,push_back}
- Since
- version 1.0.0
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add an object to an object
Inserts the given element val to the JSON object. If the function is called on a JSON null value, an empty object is created before inserting val.
- Parameters
-
[in] val the value to add to the JSON object
- Exceptions
-
std::domain_error when called on a type other than JSON object or null; example: "cannot use push_back() with number"
Logarithmic in the size of the container, O(log(size())).
{The example shows how push_back() and += can be used to add elements to a JSON object. Note how the null value was silently converted to a JSON object.,push_back__object_t__value}
- Since
- version 1.0.0
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inlinenoexcept |
returns an iterator to the reverse-beginning
Returns an iterator to the reverse-beginning; that is, the last element.
Constant.
This function helps basic_json satisfying the ReversibleContainer requirements:
- The complexity is constant.
- Has the semantics of
reverse_iterator(end()).
{The following code shows an example for rbegin().,rbegin}
- See also
- crbegin() – returns a const reverse iterator to the beginning
- rend() – returns a reverse iterator to the end
- crend() – returns a const reverse iterator to the end
- Since
- version 1.0.0
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inlinenoexcept |
returns a const reverse iterator to the last element
Returns a const iterator to the reverse-beginning; that is, the last element.
Constant.
This function helps basic_json satisfying the ReversibleContainer requirements:
- The complexity is constant.
- Has the semantics of
const_cast<const basic_json&>(*this).rbegin().
{The following code shows an example for crbegin().,crbegin}
- See also
- rbegin() – returns a reverse iterator to the beginning
- rend() – returns a reverse iterator to the end
- crend() – returns a const reverse iterator to the end
- Since
- version 1.0.0
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inlinenoexcept |
returns an iterator to the reverse-end
Returns an iterator to the reverse-end; that is, one before the first element.
Constant.
This function helps basic_json satisfying the ReversibleContainer requirements:
- The complexity is constant.
- Has the semantics of
reverse_iterator(begin()).
{The following code shows an example for rend().,rend}
- See also
- crend() – returns a const reverse iterator to the end
- rbegin() – returns a reverse iterator to the beginning
- crbegin() – returns a const reverse iterator to the beginning
- Since
- version 1.0.0
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inlinenoexcept |
returns a const reverse iterator to one before the first
Returns a const reverse iterator to the reverse-end; that is, one before the first element.
Constant.
This function helps basic_json satisfying the ReversibleContainer requirements:
- The complexity is constant.
- Has the semantics of
const_cast<const basic_json&>(*this).rend().
{The following code shows an example for crend().,crend}
- See also
- rend() – returns a reverse iterator to the end
- rbegin() – returns a reverse iterator to the beginning
- crbegin() – returns a const reverse iterator to the beginning
- Since
- version 1.0.0
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inlinenoexcept |
returns the number of elements
Returns the number of elements in a JSON value.
- Returns
- The return value depends on the different types and is defined as follows:
Constant, as long as array_t and object_t satisfy the Container concept; that is, their size() functions have constant complexity.Value type return value null 0boolean 1string 1number 1object result of function object_t::size() array result of function array_t::size()
This function helps basic_json satisfying the Container requirements:
{The following code calls size() on the different value types.,size}
- See also
- empty() – checks whether the container is empty
- max_size() – returns the maximal number of elements
- Since
- version 1.0.0
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inlinenoexcept |
exchanges the values
Exchanges the contents of the JSON value with those of other. Does not invoke any move, copy, or swap operations on individual elements. All iterators and references remain valid. The past-the-end iterator is invalidated.
- Parameters
-
[in,out] other JSON value to exchange the contents with
Constant.
{The example below shows how JSON values can be swapped with swap().,swap__reference}
- Since
- version 1.0.0
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inline |
exchanges the values
Exchanges the contents of a JSON array with those of other. Does not invoke any move, copy, or swap operations on individual elements. All iterators and references remain valid. The past-the-end iterator is invalidated.
- Parameters
-
[in,out] other array to exchange the contents with
- Exceptions
-
std::domain_error when JSON value is not an array; example: "cannot use swap() with string"
Constant.
{The example below shows how arrays can be swapped with swap().,swap__array_t}
- Since
- version 1.0.0
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inline |
exchanges the values
Exchanges the contents of a JSON object with those of other. Does not invoke any move, copy, or swap operations on individual elements. All iterators and references remain valid. The past-the-end iterator is invalidated.
- Parameters
-
[in,out] other object to exchange the contents with
- Exceptions
-
std::domain_error when JSON value is not an object; example: "cannot use swap() with string"
Constant.
{The example below shows how objects can be swapped with swap().,swap__object_t}
- Since
- version 1.0.0
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inline |
exchanges the values
Exchanges the contents of a JSON string with those of other. Does not invoke any move, copy, or swap operations on individual elements. All iterators and references remain valid. The past-the-end iterator is invalidated.
- Parameters
-
[in,out] other string to exchange the contents with
- Exceptions
-
std::domain_error when JSON value is not a string; example: "cannot use swap() with boolean"
Constant.
{The example below shows how strings can be swapped with swap().,swap__string_t}
- Since
- version 1.0.0
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inlinenoexcept |
return the type of the JSON value (explicit)
Return the type of the JSON value as a value from the value_t enumeration.
- Returns
- the type of the JSON value
Constant.
No-throw guarantee: this member function never throws exceptions.
{The following code exemplifies type() for all JSON types.,type}
- Since
- version 1.0.0
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inline |
access specified object element with default value
Returns either a copy of an object's element at the specified key key or a given default value if no element with key key exists.
The function is basically equivalent to executing
- Note
- Unlike at(const typename object_t::key_type&), this function does not throw if the given key key was not found.
- Unlike operator[](const typename object_t::key_type& key), this function does not implicitly add an element to the position defined by key. This function is furthermore also applicable to const objects.
- Parameters
-
[in] key key of the element to access [in] default_value the value to return if key is not found
- Template Parameters
-
ValueType type compatible to JSON values, for instance intfor JSON integer numbers,boolfor JSON booleans, orstd::vectortypes for JSON arrays. Note the type of the expected value at key and the default value default_value must be compatible.
- Returns
- copy of the element at key key or default_value if key is not found
- Exceptions
-
std::domain_error if JSON is not an object; example: "cannot use value() with null"
Logarithmic in the size of the container.
{The example below shows how object elements can be queried with a default value.,basic_json__value}
- See also
- at(const typename object_t::key_type&) for access by reference with range checking
- operator[](const typename object_t::key_type&) for unchecked access by reference
- Since
- version 1.0.0
Here is the call graph for this function: Here is the caller graph for this function:
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inline |
overload for a default value of type const char*
access specified object element with default value Returns either a copy of an object's element at the specified key key or a given default value if no element with key key exists.
The function is basically equivalent to executing
- Note
- Unlike at(const typename object_t::key_type&), this function does not throw if the given key key was not found.
- Unlike operator[](const typename object_t::key_type& key), this function does not implicitly add an element to the position defined by key. This function is furthermore also applicable to const objects.
- Parameters
-
[in] key key of the element to access [in] default_value the value to return if key is not found
- Template Parameters
-
ValueType type compatible to JSON values, for instance intfor JSON integer numbers,boolfor JSON booleans, orstd::vectortypes for JSON arrays. Note the type of the expected value at key and the default value default_value must be compatible.
- Returns
- copy of the element at key key or default_value if key is not found
- Exceptions
-
std::domain_error if JSON is not an object; example: "cannot use value() with null"
Logarithmic in the size of the container.
{The example below shows how object elements can be queried with a default value.,basic_json__value}
- See also
- at(const typename object_t::key_type&) for access by reference with range checking
- operator[](const typename object_t::key_type&) for unchecked access by reference
- Since
- version 1.0.0
Here is the call graph for this function:Friends And Related Function Documentation
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friend |
comparison: not equal
Compares two JSON values for inequality by calculating not (lhs == rhs).
- Parameters
-
[in] lhs first JSON value to consider [in] rhs second JSON value to consider
- Returns
- whether the values lhs and rhs are not equal
Linear.
{The example demonstrates comparing several JSON types.,operator__notequal}
- Since
- version 1.0.0
|
friend |
comparison: not equal
The functions compares the given JSON value against a null pointer. As the null pointer can be used to initialize a JSON value to null, a comparison of JSON value v with a null pointer should be equivalent to call not v.is_null().
- Parameters
-
[in] v JSON value to consider
- Returns
- whether v is not null
Constant.
{The example compares several JSON types to the null pointer. ,operator__notequal__nullptr_t}
- Since
- version 1.0.0
|
friend |
comparison: not equal
comparison: not equal The functions compares the given JSON value against a null pointer. As the null pointer can be used to initialize a JSON value to null, a comparison of JSON value v with a null pointer should be equivalent to call not v.is_null().
- Parameters
-
[in] v JSON value to consider
- Returns
- whether v is not null
Constant.
{The example compares several JSON types to the null pointer. ,operator__notequal__nullptr_t}
- Since
- version 1.0.0
|
friend |
comparison operator for JSON types
Returns an ordering that is similar to Python:
- order: null < boolean < number < object < array < string
- furthermore, each type is not smaller than itself
- Since
- version 1.0.0
|
friend |
comparison: less than
Compares whether one JSON value lhs is less than another JSON value rhs according to the following rules:
- If lhs and rhs have the same type, the values are compared using the default
<operator. - Integer and floating-point numbers are automatically converted before comparison
- In case lhs and rhs have different types, the values are ignored and the order of the types is considered, see operator<(const value_t, const value_t).
- Parameters
-
[in] lhs first JSON value to consider [in] rhs second JSON value to consider
- Returns
- whether lhs is less than rhs
Linear.
{The example demonstrates comparing several JSON types.,operator__less}
- Since
- version 1.0.0
|
friend |
serialize to stream
Serialize the given JSON value j to the output stream o. The JSON value will be serialized using the dump member function. The indentation of the output can be controlled with the member variable width of the output stream o. For instance, using the manipulator std::setw(4) on o sets the indentation level to 4 and the serialization result is the same as calling dump(4).
- Parameters
-
[in,out] o stream to serialize to [in] j JSON value to serialize
- Returns
- the stream o
Linear.
{The example below shows the serialization with different parameters to width to adjust the indentation level.,operator_serialize}
- Since
- version 1.0.0
|
friend |
deserialize from stream
Deserializes an input stream to a JSON value.
- Parameters
-
[in,out] i input stream to read a serialized JSON value from [in,out] j JSON value to write the deserialized input to
- Exceptions
-
std::invalid_argument in case of parse errors
Linear in the length of the input. The parser is a predictive LL(1) parser.
- Note
- A UTF-8 byte order mark is silently ignored.
{The example below shows how a JSON value is constructed by reading a serialization from a stream.,operator_deserialize}
- See also
- parse(std::istream&, parser_callback_t) for a variant with a parser callback function to filter values while parsing
- Since
- version 1.0.0
|
friend |
comparison: less than or equal
Compares whether one JSON value lhs is less than or equal to another JSON value by calculating not (rhs < lhs).
- Parameters
-
[in] lhs first JSON value to consider [in] rhs second JSON value to consider
- Returns
- whether lhs is less than or equal to rhs
Linear.
{The example demonstrates comparing several JSON types.,operator__greater}
- Since
- version 1.0.0
|
friend |
comparison: equal
Compares two JSON values for equality according to the following rules:
- Two JSON values are equal if (1) they are from the same type and (2) their stored values are the same.
- Integer and floating-point numbers are automatically converted before comparison. Floating-point numbers are compared indirectly: two floating-point numbers
f1andf2are considered equal if neitherf1 > f2norf2 > f1holds. - Two JSON null values are equal.
- Parameters
-
[in] lhs first JSON value to consider [in] rhs second JSON value to consider
- Returns
- whether the values lhs and rhs are equal
Linear.
{The example demonstrates comparing several JSON types.,operator__equal}
- Since
- version 1.0.0
|
friend |
comparison: equal
The functions compares the given JSON value against a null pointer. As the null pointer can be used to initialize a JSON value to null, a comparison of JSON value v with a null pointer should be equivalent to call v.is_null().
- Parameters
-
[in] v JSON value to consider
- Returns
- whether v is null
Constant.
{The example compares several JSON types to the null pointer. ,operator__equal__nullptr_t}
- Since
- version 1.0.0
|
friend |
comparison: equal
comparison: equal The functions compares the given JSON value against a null pointer. As the null pointer can be used to initialize a JSON value to null, a comparison of JSON value v with a null pointer should be equivalent to call v.is_null().
- Parameters
-
[in] v JSON value to consider
- Returns
- whether v is null
Constant.
{The example compares several JSON types to the null pointer. ,operator__equal__nullptr_t}
- Since
- version 1.0.0
|
friend |
comparison: greater than
Compares whether one JSON value lhs is greater than another JSON value by calculating not (lhs <= rhs).
- Parameters
-
[in] lhs first JSON value to consider [in] rhs second JSON value to consider
- Returns
- whether lhs is greater than to rhs
Linear.
{The example demonstrates comparing several JSON types.,operator__lessequal}
- Since
- version 1.0.0
|
friend |
comparison: greater than or equal
Compares whether one JSON value lhs is greater than or equal to another JSON value by calculating not (lhs < rhs).
- Parameters
-
[in] lhs first JSON value to consider [in] rhs second JSON value to consider
- Returns
- whether lhs is greater than or equal to rhs
Linear.
{The example demonstrates comparing several JSON types.,operator__greaterequal}
- Since
- version 1.0.0
|
friend |
serialize to stream
serialize to stream Serialize the given JSON value j to the output stream o. The JSON value will be serialized using the dump member function. The indentation of the output can be controlled with the member variable width of the output stream o. For instance, using the manipulator std::setw(4) on o sets the indentation level to 4 and the serialization result is the same as calling dump(4).
- Parameters
-
[in,out] o stream to serialize to [in] j JSON value to serialize
- Returns
- the stream o
Linear.
{The example below shows the serialization with different parameters to width to adjust the indentation level.,operator_serialize}
- Since
- version 1.0.0
|
friend |
deserialize from stream
deserialize from stream Deserializes an input stream to a JSON value.
- Parameters
-
[in,out] i input stream to read a serialized JSON value from [in,out] j JSON value to write the deserialized input to
- Exceptions
-
std::invalid_argument in case of parse errors
Linear in the length of the input. The parser is a predictive LL(1) parser.
- Note
- A UTF-8 byte order mark is silently ignored.
{The example below shows how a JSON value is constructed by reading a serialization from a stream.,operator_deserialize}
- See also
- parse(std::istream&, parser_callback_t) for a variant with a parser callback function to filter values while parsing
- Since
- version 1.0.0
The documentation for this class was generated from the following file:
- /home/lemniscate/workspace/PFPSim/pfpsim/core/json.hpp