template<typename PointerType> PointerType get_ptr() noexcept; template<typename PointerType> constexpr const PointerType get_ptr() const noexcept;
Implicit pointer access to the internally stored JSON value. No copies are made.
PointerType : pointer type; must be a pointer to array_t, object_t, string_t, boolean_t, number_integer_t, or number_unsigned_t, number_float_t, or binary_t. Other types will not compile.
pointer to the internally stored JSON value if the requested pointer type fits to the JSON value; #!cpp nullptr otherwise
No-throw guarantee: this function never throws exceptions.
Constant.
!!! danger “Undefined behavior”
The pointer becomes invalid if the underlying JSON object changes.
Consider the following example code where the pointer `ptr` changes after the array is resized. As a result,
reading or writing to `ptr` after the array change would be undefined behavior. The address of the first array
element changes, because the underlying `std::vector` is resized after adding a fifth element.
```cpp
#include <iostream>
#include <nlohmann/json.hpp>
using json = nlohmann::json;
int main()
{
json j = {1, 2, 3, 4};
auto* ptr = j[0].get_ptr<std::int64_t*>();
std::cout << "value at " << ptr << " is " << *ptr << std::endl;
j.push_back(5);
ptr = j[0].get_ptr<std::int64_t*>();
std::cout << "value at " << ptr << " is " << *ptr << std::endl;
}
```
Output:
```
value at 0x6000012fc1c8 is 1
value at 0x6000029fc088 is 1
```
??? 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 `#!cpp nullptr` is returned if the value and the requested pointer type does not match. ```cpp --8<-- "examples/get_ptr.cpp" ``` Output: ```json --8<-- "examples/get_ptr.output" ```