# controller(_:didChange:atSectionIndex:for:) Notifies the receiver of the addition or removal of a section. ``` optional func controller(_ controller: NSFetchedResultsController, didChange sectionInfo: any NSFetchedResultsSectionInfo, atSectionIndex sectionIndex: Int, for type: NSFetchedResultsChangeType) ``` ## Parameters `controller` The fetched results controller that sent the message. `sectionInfo` The section that changed. `sectionIndex` The index of the changed section. `type` The type of change (insert or delete). Valid values are [`NSFetchedResultsChangeType.insert`](/documentation/CoreData/NSFetchedResultsChangeType/insert) and [`NSFetchedResultsChangeType.delete`](/documentation/CoreData/NSFetchedResultsChangeType/delete). ## Discussion The fetched results controller reports changes to its section before changes to the fetched result objects. ### Special Considerations 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. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)