allocator_type array array_t at at at at at at back back basic_json basic_json basic_json basic_json basic_json basic_json basic_json basic_json basic_json basic_json basic_json basic_json basic_json basic_json basic_json basic_json basic_json basic_json basic_json basic_json basic_json basic_json basic_json basic_json begin begin boolean_t cbegin cend clear const_pointer const_reference const_reverse_iterator count crbegin crend diff difference_type dump empty end end erase erase erase erase find find flatten front front get get get get_allocator get_ptr get_ptr get_ref get_ref insert insert insert insert insert is_array is_boolean is_discarded is_null is_number is_number_float is_number_integer is_number_unsigned is_object is_primitive is_string is_structured iterator_wrapper iterator_wrapper max_size number_float_t number_integer_t number_unsigned_t object object_t operator value_t operator ValueType operator!= operator!= operator!= operator+= operator+= operator+= operator+= operator< operator< operator<< operator<< operator<= operator= operator== operator== operator== operator> operator>= operator>> operator>> operator[] operator[] operator[] operator[] operator[] operator[] operator[] operator[] operator[] operator[] parse parse parse parse_event_t parser_callback_t patch pointer push_back push_back push_back push_back rbegin rbegin reference rend rend reverse_iterator size size_type string_t swap swap swap swap type unflatten value value value value value_t value_type ~basic_json

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> 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. Note The class invariant is satisfied, because it poses no requirements for null values. 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. #include <json.hpp> using json = nlohmann::json; int main() { // create a JSON value with default null value json j; // serialize the JSON null value std::cout << j << '\n'; } 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