JSON for Modern C++ 2.1.1
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◆ operator+=() [3/4]

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, template< typename T, typename SFINAE=void > class JSONSerializer = adl_serializer>
reference nlohmann::basic_json< ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType, JSONSerializer >::operator+= ( const typename object_t::value_type &  val)
inline

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]valthe value to add to the JSON object
Exceptions
std::domain_errorwhen called on a type other than JSON object or null; example: "cannot use push_back() with number"
Complexity\n Logarithmic in the size of the container, O(log(size())).
Example\n 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.
1#include <json.hpp>
2
3using json = nlohmann::json;
4
5int main()
6{
7 // create JSON values
8 json object = {{"one", 1}, {"two", 2}};
9 json null;
10
11 // print values
12 std::cout << object << '\n';
13 std::cout << null << '\n';
14
15 // add values
16 object.push_back(json::object_t::value_type("three", 3));
17 object += json::object_t::value_type("four", 4);
18 null += json::object_t::value_type("A", "a");
19 null += json::object_t::value_type("B", "b");
20
21 // print values
22 std::cout << object << '\n';
23 std::cout << null << '\n';
24}
basic_json value_type
the type of elements in a basic_json container
Definition json.hpp:1067
static basic_json array(std::initializer_list< basic_json > init=std::initializer_list< basic_json >())
explicitly create an array from an initializer list
Definition json.hpp:2165
a class to store JSON values
Definition json.hpp:1040
basic_json<> json
default JSON class
Definition json.hpp:12369

Output (play with this example online):
{"one":1,"two":2}
null
{"four":4,"one":1,"three":3,"two":2}
{"A":"a","B":"b"}

The example code above can be translated with
g++ -std=c++11 -Isrc doc/examples/push_back__object_t__value.cpp -o push_back__object_t__value 
Since
version 1.0.0

Definition at line 5368 of file json.hpp.