👀 Views: 348 💬 Answers: 1 📅 Created: 2025-06-12

ios core-data combine uicollectionview Swift

I'm reviewing some code and I've been struggling with this for a few days now and could really use some help... I'm working on an iOS 16 app that utilizes Core Data with `NSFetchedResultsController` to manage and display data in a `UICollectionView`. However, I've run into an scenario where the UI does not update when the underlying data changes. I'm using Combine to observe changes and update the view accordingly. Here's a brief overview of what I've implemented: In my view model, I'm setting up the `NSFetchedResultsController` like this: ```swift let fetchRequest: NSFetchRequest<Item> = Item.fetchRequest() fetchRequest.sortDescriptors = [NSSortDescriptor(key: "date", ascending: false)] let fetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: context, sectionNameKeyPath: nil, cacheName: nil) fetchedResultsController.delegate = self try? fetchedResultsController.performFetch() ``` I also have a Combine publisher that listens to changes in the context: ```swift let contextPublisher = NotificationCenter.default.publisher(for: .NSManagedObjectContextObjectsDidChange, object: context) .sink { [weak self] _ in self?.updateData() } ``` The `updateData` method calls `performFetch` on the `fetchedResultsController`, but the UI remains unchanged. I've ensured that my data source methods for the `UICollectionView` are set up correctly and are referencing the fetched results controller's `fetchedObjects` property. ```swift func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int { return fetchedResultsController.sections?[section].numberOfObjects ?? 0 } func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell { let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Cell", for: indexPath) let item = fetchedResultsController.object(at: indexPath) // Configure the cell with item return cell } ``` The `NSFetchedResultsControllerDelegate` methods aren't being called either, which makes me think the controller is not aware of changes in the context. I've confirmed that changes are indeed made to the managed object context. I've also tried reloading the collection view in the `updateData` method, but it still does not reflect changes. The console does not show any behavior messages, making troubleshooting a bit harder. Can someone guide to identify what I'm missing here, or if there's a better way to combine `NSFetchedResultsController` with Combine in this context? Thanks for your help in advance! I'm working with Swift in a Docker container on Linux. I'd really appreciate any guidance on this.