Provides an opportunity to respond when a change is about to be made to a specified to-many relationship.
- iOS 3.0+
- macOS 10.4+
- tvOS 9.0+
- watchOS 2.0+
- Core Data
The name of a property that is a to-many relationship
The type of change that will be made.
The objects that were involved in the change (see
Value Set Mutation Kind
For more details, see Key-Value Observing Programming Guide.
You must not override this method.