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 >::value, int >::type = 0>
PointerType nlohmann::basic_json::get_ptr | ( |  | ) |
| inlinenoexcept
  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