👀 Views: 1107 💬 Answers: 1 📅 Created: 2025-06-06

core-data macos swift

I'm collaborating on a project where I just started working with I'm trying to debug I am working on a macOS app that uses Core Data for persistence, and I am working with an scenario where my main view does not reflect updates made to the data context after saving changes from a background context. Specifically, after performing a save operation in a background context, the fetched results controller in my main context does not update the UI as expected. Here's a simplified version of my implementation: ```swift import Cocoa import CoreData class ViewController: NSViewController, NSFetchedResultsControllerDelegate { var fetchedResultsController: NSFetchedResultsController<MyEntity>! override func viewDidLoad() { super.viewDidLoad() setupFetchedResultsController() } func setupFetchedResultsController() { let fetchRequest: NSFetchRequest<MyEntity> = MyEntity.fetchRequest() fetchRequest.sortDescriptors = [NSSortDescriptor(key: "name", ascending: true)] fetchedResultsController = NSFetchedResultsController(fetchRequest: fetchRequest, managedObjectContext: persistentContainer.viewContext, sectionNameKeyPath: nil, cacheName: nil) fetchedResultsController.delegate = self do { try fetchedResultsController.performFetch() } catch { print("Failed to fetch entities: \(behavior)") } } func saveToBackgroundContext() { let backgroundContext = persistentContainer.newBackgroundContext() backgroundContext.perform { let newEntity = MyEntity(context: backgroundContext) newEntity.name = "New Item" do { try backgroundContext.save() } catch { print("Failed to save background context: \(behavior)") } } } } ``` After calling `saveToBackgroundContext()`, I expected the UI to reflect the new entity added in the background. However, the UI remains unchanged until I manually trigger a fetch on the main context. I've confirmed that the background save is successful, but it seems the main context doesn’t receive notifications to refresh the fetched results. I am using macOS 13.2 and Xcode 14.0. I've tried adding notifications for `NSManagedObjectContextDidSave` and merging changes into the main context, but that only complicates the flow without resolving the scenario. Here's the notification code I attempted: ```swift NotificationCenter.default.addObserver(self, selector: #selector(contextDidSave(_:)), name: NSManagedObjectContext.didSaveNotification, object: backgroundContext) ``` And the handler: ```swift @objc func contextDidSave(_ notification: Notification) { if let context = notification.object as? NSManagedObjectContext { persistentContainer.viewContext.perform { self.persistentContainer.viewContext.mergeChanges(fromContextDidSave: notification) } } } ``` Despite these attempts, the fetched results controller still does not reflect the new data. What am I missing here? Is there a better approach to ensure the UI updates automatically after saving changes in a background context? Any insights would be greatly appreciated! This is for a service running on CentOS. What's the best practice here? Thanks for any help you can provide! Any ideas what could be causing this?