Informs the observed object that the specified change is about to be made to a specified unordered to-many relationship.
- iOS 2.0+
- macOS 10.4+
- UIKit for Mac 13.0+Beta
- tvOS 9.0+
- watchOS 2.0+
The name of a property that is an unordered to-many relationship
The type of change that will be made.
The objects that are involved in the change (see
Value Set Mutation Kind
Use this method when implementing key-value observer compliance manually.
You rarely need to override this method in subclasses, but if you do, be sure to call