Informs the observed object that the specified change is about to be executed at given indexes for a specified ordered to-many relationship.
- iOS 2.0+
- macOS 10.3+
- tvOS 9.0+
- watchOS 2.0+
The type of change that is about to be made.
The indexes of the to-many relationship that will be affected by the change.
The name of a property that is an ordered to-many relationship.
Use this method when implementing key-value-observing compliance manually.
You rarely need to override this method in subclasses, but if you do, be sure to call