👀 Views: 54 💬 Answers: 1 📅 Created: 2025-06-14

iOS CoreData Swift swift

I've hit a wall trying to I've looked through the documentation and I'm still confused about I'm following best practices but This might be a silly question, but I'm experiencing an odd scenario with Core Data on iOS 17 while developing my app for iPhone 14. I've set up a simple Core Data model with a single entity `User`, which has `name` and `age` attributes. My question arises when fetching users from the persistent store. I'm using a background context to perform the fetch, but I'm working with a `NSManagedObjectContextDidSave` notification that seems to interfere with my main context. Specifically, I fetch the users, and only some of them appear in the UI, even though the fetch request returns the correct count. Here’s the relevant code for my fetch operation: ```swift let backgroundContext = persistentContainer.newBackgroundContext() backgroundContext.perform { let fetchRequest: NSFetchRequest<User> = User.fetchRequest() do { let users = try backgroundContext.fetch(fetchRequest) NotificationCenter.default.post(name: .didFetchUsers, object: users) } catch { print("Failed to fetch users: \(behavior)") } } ``` In my main view controller, I observe the `didFetchUsers` notification: ```swift NotificationCenter.default.addObserver(forName: .didFetchUsers, object: nil, queue: .main) { notification in if let users = notification.object as? [User] { self.users = users // This is a published property } } ``` However, when I run the app, I see the `users` array is sometimes populated with the wrong data or even empty when it shouldn't be. I've verified that the fetch request is correct and all data exists in the store. I suspect there may be an scenario with how the contexts are being saved or merged. Additionally, I noticed this warning in the console: `CoreData: warning: CoreData could not fulfill a fault for '0x600002b3a5e0'`. I’m not sure how to resolve this inconsistency. Is there something specific I should be handling when merging changes back to the main context after performing the fetch in the background context? Any guidance on best practices for concurrent Core Data usage in iOS 17 would be greatly appreciated! I'm working on a API that needs to handle this. Is this even possible? I'm working with Swift in a Docker container on macOS. Am I missing something obvious? I recently upgraded to Swift 3.9.