JSON for Modern C++  3.7.0

◆ get() [5/6]

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 PointerType , typename std::enable_if< std::is_pointer< PointerType >::value, int >::type = 0>
auto nlohmann::basic_json::get ( ) -> decltype(std::declval<basic_json_t&>().template get_ptr<PointerType>())
inlinenoexcept

Explicit pointer access to the internally stored JSON value. No copies are made.

Warning
The pointer becomes invalid if the underlying JSON object changes.
Template Parameters
PointerTypepointer type; must be a pointer to array_t, object_t, string_t, boolean_t, number_integer_t, number_unsigned_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 <iostream>
2 #include <nlohmann/json.hpp>
3 
4 using json = nlohmann::json;
5 
6 int main()
7 {
8  // create a JSON number
9  json value = 17;
10 
11  // explicitly getting pointers
12  auto p1 = value.get<const json::number_integer_t*>();
13  auto p2 = value.get<json::number_integer_t*>();
14  auto p3 = value.get<json::number_integer_t* const>();
15  auto p4 = value.get<const json::number_integer_t* const>();
16  auto p5 = value.get<json::number_float_t*>();
17 
18  // print the pointees
19  std::cout << *p1 << ' ' << *p2 << ' ' << *p3 << ' ' << *p4 << '\n';
20  std::cout << std::boolalpha << (p5 == nullptr) << '\n';
21 }
NumberFloatType number_float_t
a type for a number (floating-point)
Definition: json.hpp:15225
basic_json<> json
default JSON class
Definition: json.hpp:2355
NumberIntegerType number_integer_t
a type for a number (integer)
Definition: json.hpp:15086
ValueType value(const typename object_t::key_type &key, const ValueType &default_value) const
access specified object element with default value
Definition: json.hpp:17829

Output (play with this example online):
17 17 17 17
true
The example code above can be translated with
g++ -std=c++11 -Isingle_include doc/examples/get__PointerType.cpp -o get__PointerType 
See also
get_ptr() for explicit pointer-member access
Since
version 1.0.0

Definition at line 17184 of file json.hpp.