JSON for Modern C++ 3.0

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~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 NumberFloatType = double, template< typename U > class AllocatorType = std::allocator> template<typename PointerType , typename std::enable_if< std::is_pointer< PointerType >::valueand std::is_const< PointerType >::value, int >::type = 0>
const PointerType nlohmann::basic_json::get_ptr | ( |  | ) | const
| inlinenoexcept
  get a pointer value (implicit) Implict pointer access to the internally stored JSON value. No copies are made. Warning Writing data to the pointee of the result yields an undefined state. Template Parameters
  PointerType | pointer type; must be a pointer to array_t, object_t, string_t, boolean_t, number_integer_t, or number_float_t.
  Returns pointer to the internally stored JSON value if the requested pointer type PointerType fits to the JSON value; `nullptr` otherwise Complexity Constant. Example The example below shows how pointers to internal values of a JSON value can be requested. Note that no type conversions are made and a `nullptr` is returned if the value and the requested pointer type does not match. 1 #include <json.hpp> 2 3 using namespace nlohmann; 4 5 int main() 6 { 7 // create a JSON boolean 8 json value = 17; 9 10 // explicitly getting pointers 11 auto p1 = value.get_ptr<const json::number_integer_t*>(); 12 auto p2 = value.get_ptr<json::number_integer_t*>(); 13 auto p3 = value.get_ptr<json::number_integer_t* const>(); 14 auto p4 = value.get_ptr<const json::number_integer_t* const>(); 15 auto p5 = value.get_ptr<json::number_float_t*>(); 16 17 // print the pointees 18 std::cout << *p1 << ' ' << *p2 << ' ' << *p3 << ' ' << *p4 << '\n'; 19 std::cout << std::boolalpha << (p5 == nullptr) << '\n'; 20 } nlohmann::basic_json a class to store JSON values Definition: json.hpp:130 nlohmann namespace for Niels Lohmann Definition: json.hpp:55 nlohmann::basic_json::get_ptr PointerType get_ptr() noexcept get a pointer value (implicit) Definition: json.hpp:2328 nlohmann::basic_json::number_integer_t NumberIntegerType number_integer_t a type for a number (integer) Definition: json.hpp:435 nlohmann::basic_json::number_float_t NumberFloatType number_float_t a type for a number (floating-point) Definition: json.hpp:495 Output (play with this example online):
      17 17 17 17
      true
  The example code above can be translated with
      g++ -std=c++11 -Isrc doc/examples/get_ptr.cpp -o get_ptr