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 begin begin boolean_t cbegin cend clear const_iterator const_pointer const_reference const_reverse_iterator count crbegin crend detail::external_constructor diff difference_type dump emplace emplace_back empty end end erase erase erase erase exception find find flatten from_cbor from_msgpack front front get get get get get get_allocator get_ptr get_ptr get_ref get_ref insert insert insert insert insert insert invalid_iterator 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 iterator_wrapper iterator_wrapper json_serializer max_size meta 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[] operator[] operator[] operator[] operator[] operator[] operator[] operator[] other_error out_of_range parse parse parse parse parse parse parse_error 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 to_cbor to_msgpack type type_error type_name unflatten value value value value value_t value_type ~basic_json

operator ValueType() 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> template<typename ValueType , typename std::enable_if< not std::is_pointer< ValueType >::value and not std::is_same< ValueType, typename string_t::value_type >::value and not std::is_same< ValueType, std::initializer_list< typename string_t::value_type >>::value, int >::type = 0> nlohmann::basic_json::operator ValueType ( ) const inline Implicit type conversion between the JSON value and a compatible value. The call is realized by calling get() const. Template Parameters ValueType non-pointer type compatible to the JSON value, for instance int for JSON integer numbers, bool for JSON booleans, or std::vector types for JSON arrays. The character type of string_t as well as an initializer list of this type is excluded to avoid ambiguities as these types implicitly convert to std::string. Returns copy of the JSON value, converted to type ValueType Exceptions type_error.302 in case passed type ValueType is incompatible to the JSON value type (e.g., the JSON value is of type boolean, but a string is requested); see example below Complexity Linear in the size of the JSON value. Example The example below shows several conversions from JSON values to other types. There a few things to note: (1) Floating-point numbers can be converted to integers, (2) A JSON array can be converted to a standard std::vector<short>, (3) A JSON object can be converted to C++ associative containers such as std::unordered_map<std::string, json>. #include "json.hpp" #include <unordered_map> using json = nlohmann::json; int main() { // create a JSON value with different types json json_types = { {"boolean", true}, { "number", { {"integer", 42}, {"floating-point", 17.23} } }, {"string", "Hello, world!"}, {"array", {1, 2, 3, 4, 5}}, {"null", nullptr} }; // use implicit conversions bool v1 = json_types["boolean"]; int v2 = json_types["number"]["integer"]; short v3 = json_types["number"]["integer"]; float v4 = json_types["number"]["floating-point"]; int v5 = json_types["number"]["floating-point"]; std::string v6 = json_types["string"]; std::vector<short> v7 = json_types["array"]; std::unordered_map<std::string, json> v8 = json_types; // print the conversion results std::cout << v1 << '\n'; std::cout << v2 << ' ' << v3 << '\n'; std::cout << v4 << ' ' << v5 << '\n'; std::cout << v6 << '\n'; for (auto i : v7) { std::cout << i << ' '; } std::cout << "\n\n"; for (auto i : v8) { std::cout << i.first << ": " << i.second << '\n'; } // example for an exception try { bool v1 = json_types["string"]; } catch (json::type_error& e) { std::cout << e.what() << '\n'; } } Output (play with this example online): 1 42 42 17.23 17 Hello, world! 1 2 3 4 5 string: "Hello, world!" number: {"floating-point":17.23,"integer":42} null: null boolean: true array: [1,2,3,4,5] [json.exception.type_error.302] type must be boolean, but is string The example code above can be translated with g++ -std=c++11 -Isrc doc/examples/operator__ValueType.cpp -o operator__ValueType Since version 1.0.0 Definition at line 3737 of file json.hpp.