Provides support for key-value observing access notification.
- iOS 3.0+
- macOS 10.4+
- UIKit for Mac 13.0+Beta
- tvOS 9.0+
- watchOS 2.0+
- Core Data
The name of one of the receiver's properties.
will, this method is used to fire faults, to maintain inverse relationships, and so on. Each read access must be wrapped in this method pair (in the same way that each write access must be wrapped in the
did method pair). In the default implementation of
NSManaged these methods are invoked for you automatically. If, say, you create a custom subclass that uses explicit instance variables, you must invoke them yourself, as in the following example.