JSON for Modern C++

These pages contain the API documentation of JSON for Modern C++, a C++11 header-only JSON class.

Contents

• Classes
  • basic_json – class template for JSON values
  • json – the default specialization of basic_json, defined as basic_json<>
• Functions
  • object inspection
    • dump – value serialization
    • type – type of the value
    • is_primitive , is_structured , is_null , is_boolean , is_number , is_number_integer , is_number_unsigned , is_number_float , is_object , is_array , is_string , is_discarded , is_binary – check for value type
    • operator value_t – type of the value (implicit conversion)
  • value access
    • get – get a value
    • get_ptr – get a value pointer
    • get_ref – get a value reference
    • get_binary – get a binary value
    • operator ValueType – get a value (implicit conversion)
    • value – get a value from an object and return default value if key is not present
  • exceptions
    • parse_error for exceptions indicating a parse error
    • invalid_iterator for exceptions indicating errors with iterators
    • type_error for exceptions indicating executing a member function with a wrong type
    • out_of_range for exceptions indicating access out of the defined range
    • other_error for exceptions indicating other library errors
  • lexicographical comparison operators
    • operator==
    • operator!=
    • operator<=
    • operator<
    • operator>
    • operator>=
  • serialization
    • dump serialize to string
    • operator<< serialize to stream
  • deserialization / parsing
    • parse parse from input (string, file, etc.) and return JSON value
    • sax_parse parse from input (string, file, etc.) and generate SAX events
    • operator>> parse from stream
    • accept check for syntax errors without parsing
    • SAX interface define a user-defined SAX event consumer
    • callback interface register a callback to the parse function
  • binary formats:
    • CBOR: from_cbor / to_cbor
    • MessagePack: from_msgpack / to_msgpack
    • UBJSON: from_ubjson / to_ubjson
    • BSON: from_bson / to_bson
• Types
  • arrays
  • objects
  • strings
  • booleans
  • numbers
    • signed integers
    • unsigned integers
    • floating-point
  • binary values
• further JSON standards
  • JSON Pointer (RFC 6901)
  • JSON Patch (RFC 6902)
  • JSON Merge Patch (RFC 7396)

Container function overview

The container functions known from STL have been extended to support the different value types from JSON. However, not all functions can be applied to all value types. Note that the signature of some functions differ between the types; for instance, at may be called with either a string to address a key in an object or with an integer to address a value in an array.

Note that this table only lists those exceptions thrown due to the type. For instance, the at function will always throw a json::type_error exception when called for a string type. When called for an array, it may throw an json::out_of_range exception if the passed index is invalid.

group	function	JSON value type
		object	array	string	number	boolean	null
iterators	begin	begin	begin	begin	begin	begin	begin (returns end())
	cbegin	cbegin	cbegin	cbegin	cbegin	cbegin	cbegin (returns cend())
	end	end	end	end	end	end	end
	cend	cend	cend	cend	cend	cend	cend
	rbegin	rbegin	rbegin	rbegin	rbegin	rbegin	rbegin
	crbegin	crbegin	crbegin	crbegin	crbegin	crbegin	crbegin
	rend	rend	rend	rend	rend	rend	rend
	crend	crend	crend	crend	crend	crend	crend
element access	at	at	at	throws json::type_error (304)	throws json::type_error (304)	throws json::type_error (304)	throws json::type_error (304)
	operator[]	operator[]	operator[]	throws json::type_error (305)	throws json::type_error (305)	throws json::type_error (305)	operator[] (creates object) operator[] (creates array)
	front	front	front	front	front	front	throws json::invalid_iterator (214)
	back	back	back	back	back	back	throws json::invalid_iterator (214)
capacity	empty	empty	empty	empty (returns false)	empty (returns false)	empty (returns false)	empty (returns true)
	size	size	size	size (returns 1)	size (returns 1)	size (returns 1)	size (returns 0)
	max_size_	max_size	max_size	max_size (returns 1)	max_size (returns 1)	max_size (returns 1)	max_size (returns 0)
modifiers	clear	clear	clear	clear	clear	clear	clear
	insert	throws json::type_error (309)	insert	throws json::type_error (309)	throws json::type_error (309)	throws json::type_error (309)	throws json::type_error (309)
	erase	erase	erase	erase (converts to null)	erase (converts to null)	erase (converts to null)	throws json::type_error (307)
	push_back	push_back	push_back	throws json::type_error (308)	throws json::type_error (308)	throws json::type_error (308)	push_back (creates object) push_back (creates array)
	emplace / emplace_back	emplace	emplace_back	throws json::type_error (311)	throws json::type_error (311)	throws json::type_error (311)	emplace (creates object) emplace_back (creates array)
	update	update	throws json::type_error (312)	throws json::type_error (312)	throws json::type_error (312)	throws json::type_error (312)	throws json::type_error (312)
	swap	swap	swap	swap	swap	swap	swap
lookup	find	find	find (returns end())	find (returns end())	find (returns end())	find (returns end())	find (returns end())
	count	count	count (returns 0)	count (returns 0)	count (returns 0)	count (returns 0)	count (returns 0)
	contains	contains	contains (returns false)	contains (returns false)	contains (returns false)	contains (returns false)	contains (returns false)

Copyright

Copyright © 2013-2020 Niels Lohmann. The code is licensed under the MIT License.

Author

Niels Lohmann

See also

https://github.com/nlohmann/json to download the source code

Version

3.9.1