JSON for Modern C++  2.0.0
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 = int64_t, class NumberUnsignedType = uint64_t, class NumberFloatType = double, template< typename U > class AllocatorType = std::allocator>
nlohmann::basic_json::basic_json ( )
default

Create a null JSON value. This is the implicit version of the null value constructor as it takes no parameters.

Complexity
Constant.
Exception safety
No-throw guarantee: this constructor never throws exceptions.
Requirements
This function helps basic_json satisfying the Container requirements:
  • The complexity is constant.
  • As postcondition, it holds: basic_json().empty() == true.
Example
The following code shows the constructor for a null JSON value.
1 #include <json.hpp>
2 
3 using json = nlohmann::json;
4 
5 int main()
6 {
7  // create a JSON value with default null value
8  json j;
9 
10  // serialize the JSON null value
11  std::cout << j << '\n';
12 }
basic_json<> json
default JSON class
Definition: json.hpp:8653
Output (play with this example online):
null
The example code above can be translated with
g++ -std=c++11 -Isrc doc/examples/basic_json.cpp -o basic_json 
See also
basic_json(std::nullptr_t) – create a null value
Since
version 1.0.0