Notifies the receiver of the addition or removal of a section.
- iOS 4.0+
- macOS 10.12+
- tvOS 9.0+
- watchOS 2.0+
- Core Data
The fetched results controller that sent the message.
The section that changed.
The index of the changed section.
The fetched results controller reports changes to its section before changes to the fetched result objects.
This method may be invoked many times during an update event (for example, if you are importing data on a background thread and adding them to the context in a batch). You should consider carefully whether you want to update the table view on receipt of each message.