allocator_type array array_t 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 begin begin boolean_t cbegin cend clear const_pointer const_reference const_reverse_iterator count crbegin crend difference_type dump empty end end erase erase erase erase find find 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[] parse parse parse parse_event_t parser_callback_t pointer push_back push_back push_back rbegin rbegin reference rend rend reverse_iterator size size_type string_t swap swap swap swap type 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 = int64_t, class NumberUnsignedType = uint64_t, class NumberFloatType = double, template< typename U > class AllocatorType = std::allocator> bool nlohmann::basic_json< ObjectType, ArrayType, StringType, BooleanType, NumberIntegerType, NumberUnsignedType, NumberFloatType, AllocatorType >::is_null ( ) const inlinenoexcept This function returns true iff the JSON value is null. Returns true if type is null, false otherwise. Complexity Constant. Example The following code exemplifies is_null for all JSON types. #include <json.hpp> using json = nlohmann::json; int main() { // create JSON values json j_null; json j_boolean = true; json j_number_integer = 17; json j_number_unsigned_integer = 12345678987654321u; json j_number_float = 23.42; json j_object = {{"one", 1}, {"two", 2}}; json j_array = {1, 2, 4, 8, 16}; json j_string = "Hello, world"; // call is_null() std::cout << std::boolalpha; std::cout << j_null.is_null() << '\n'; std::cout << j_boolean.is_null() << '\n'; std::cout << j_number_integer.is_null() << '\n'; std::cout << j_number_unsigned_integer.is_null() << '\n'; std::cout << j_number_float.is_null() << '\n'; std::cout << j_object.is_null() << '\n'; std::cout << j_array.is_null() << '\n'; std::cout << j_string.is_null() << '\n'; } Output (play with this example online): true false false false false false false false The example code above can be translated with g++ -std=c++11 -Isrc doc/examples/is_null.cpp -o is_null Since version 1.0.0 Definition at line 2148 of file json.hpp.