JSON for Modern C++  3.7.2

◆ push_back() [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>
void nlohmann::basic_json::push_back ( const typename object_t::value_type &  val)
inline

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
type_error.308when called on a type other than JSON object or null; example: "cannot use push_back() with number"
Complexity
Logarithmic in the size of the container, O(log(size())).
Example
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 <iostream>
2 #include <nlohmann/json.hpp>
3 
4 using json = nlohmann::json;
5 
6 int main()
7 {
8  // create JSON values
9  json object = {{"one", 1}, {"two", 2}};
10  json null;
11 
12  // print values
13  std::cout << object << '\n';
14  std::cout << null << '\n';
15 
16  // add values
17  object.push_back(json::object_t::value_type("three", 3));
18  object += json::object_t::value_type("four", 4);
19  null += json::object_t::value_type("A", "a");
20  null += json::object_t::value_type("B", "b");
21 
22  // print values
23  std::cout << object << '\n';
24  std::cout << null << '\n';
25 }

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 -Isingle_include doc/examples/push_back__object_t__value.cpp -o push_back__object_t__value 
Since
version 1.0.0

Definition at line 19505 of file json.hpp.

nlohmann::json
basic_json<> json
default JSON class
Definition: json.hpp:2445