A set of strings, with each string specifying a tag used to mark on-demand resources managed by the request. (read-only)
- iOS 9.0+
- UIKit for Mac 13.0+Beta
- tvOS 9.0+
- watchOS 2.0+
This value is read-only value and is set when the resource request is initialized. The value of each tag in the set corresponds to an identifier you created during app development.