Tells the client that a cached response is valid.
- iOS 2.0+
- macOS 10.2+
- UIKit for Mac 13.0+Beta
- tvOS 9.0+
- watchOS 2.0+
The URL protocol object sending the message.
The cached response whose validity is being communicated.
This documentation contains preliminary information about an API or technology in development. This information is subject to change, and software implemented according to this documentation should be tested with final operating system software.Learn more about using Apple's beta software