JSON for Modern C++  3.7.2

◆ object()

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>
static basic_json nlohmann::basic_json::object ( initializer_list_t  init = {})
inlinestatic

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(initializer_list_t), 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(initializer_list_t, bool, value_t).
Parameters
[in]initinitializer list to create an object from (optional)
Returns
JSON object value
Exceptions
type_error.301if init is not a list of pairs whose first elements are strings. In this case, no object can be created. When such a value is passed to basic_json(initializer_list_t, bool, value_t), an array would have been created from the passed initializer list init. See example below.
Complexity
Linear in the size of init.
Exception safety
Strong guarantee: if an exception is thrown, there are no changes to any JSON value.
Example
The following code shows an example for the object function.
1 #include <iostream>
2 #include <nlohmann/json.hpp>
3 
4 using json = nlohmann::json;
5 
6 int main()
7 {
8  // create JSON objects
9  json j_no_init_list = json::object();
10  json j_empty_init_list = json::object({});
11  json j_list_of_pairs = json::object({ {"one", 1}, {"two", 2} });
12 
13  // serialize the JSON objects
14  std::cout << j_no_init_list << '\n';
15  std::cout << j_empty_init_list << '\n';
16  std::cout << j_list_of_pairs << '\n';
17 
18  // example for an exception
19  try
20  {
21  // can only create an object from a list of pairs
22  json j_invalid_object = json::object({{ "one", 1, 2 }});
23  }
24  catch (json::type_error& e)
25  {
26  std::cout << e.what() << '\n';
27  }
28 }

Output (play with this example online):
{}
{}
{"one":1,"two":2}
[json.exception.type_error.301] cannot create object from initializer list
The example code above can be translated with
g++ -std=c++11 -Isingle_include doc/examples/object.cpp -o object 
See also
basic_json(initializer_list_t, bool, value_t) – create a JSON value from an initializer list
array(initializer_list_t) – create a JSON array value from an initializer list
Since
version 1.0.0

Definition at line 16135 of file json.hpp.

nlohmann::basic_json::object
static basic_json object(initializer_list_t init={})
explicitly create an object from an initializer list
Definition: json.hpp:16135
nlohmann::basic_json::type_error
detail::type_error type_error
exception indicating executing a member function with a wrong type
Definition: json.hpp:14780
nlohmann::json
basic_json<> json
default JSON class
Definition: json.hpp:2445