Retains a Core Foundation object.
- iOS 2.0+
- macOS 10.0+
- tvOS 9.0+
- watchOS 2.0+
- Core Foundation
The CFType object to retain. This value must not be
The input value,
You should retain a Core Foundation object when you receive it from elsewhere (that is, you did not create or copy it) and you want it to persist. If you retain a Core Foundation object you are responsible for releasing it (see Memory Management Programming Guide for Core Foundation).
NULL, this will cause a runtime error and your application will crash.