# nlohmann::basic_json::get_ptr
```cpp
template
PointerType get_ptr() noexcept;
template
constexpr const PointerType get_ptr() const noexcept;
```
Implicit pointer access to the internally stored JSON value. No copies are made.
## Template parameters
`PointerType`
: pointer type; must be a pointer to [`array_t`](array_t.md), [`object_t`](object_t.md), [`string_t`](string_t.md),
[`boolean_t`](boolean_t.md), [`number_integer_t`](number_integer_t.md), or
[`number_unsigned_t`](number_unsigned_t.md), [`number_float_t`](number_float_t.md), or [`binary_t`](binary_t.md).
Other types will not compile.
## Return value
pointer to the internally stored JSON value if the requested pointer type fits to the JSON value; `#!cpp nullptr`
otherwise
## Exception safety
No-throw guarantee: this function never throws exceptions.
## Complexity
Constant.
## Notes
!!! 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
#include
using json = nlohmann::json;
int main()
{
json j = {1, 2, 3, 4};
auto* ptr = j[0].get_ptr();
std::cout << "value at " << ptr << " is " << *ptr << std::endl;
j.push_back(5);
ptr = j[0].get_ptr();
std::cout << "value at " << ptr << " is " << *ptr << std::endl;
}
```
Output:
```
value at 0x6000012fc1c8 is 1
value at 0x6000029fc088 is 1
```
## Examples
??? 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"
```
## See also
- [get_ref()](get_ref.md) get a reference value
## Version history
- Added in version 1.0.0.
- Extended to binary types in version 3.8.0.