👀 Views: 465 💬 Answers: 1 📅 Created: 2025-06-06

Objective-C SwiftUI NSFetchedResultsController

I'm working on an Objective-C project that integrates a SwiftUI view for displaying data fetched using NSFetchedResultsController. Everything seemed to be going smoothly until I encountered an EXC_BAD_ACCESS error when the SwiftUI view tries to access the data. I suspect it might be related to how I'm observing the changes from NSFetchedResultsController. Here’s a snippet of the code: ```objc @property (nonatomic, strong) NSFetchedResultsController *fetchedResultsController; - (void)setupFetchedResultsController { NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"EntityName"]; fetchRequest.sortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey:@"attribute" ascending:YES]]; self.fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:nil]; NSError *error = nil; if (![self.fetchedResultsController performFetch:&error]) { NSLog(@"Unresolved error %@", error); } } ``` In my SwiftUI view, I am trying to access the fetched objects like this: ```swift struct ContentView: View { @ObservedObject var viewModel: YourViewModel var body: some View { List(viewModel.items) { item in Text(item.name) } } } ``` The `YourViewModel` class is bridging between the NSFetchedResultsController and the SwiftUI view. I have implemented the delegate methods for NSFetchedResultsController as follows: ```objc - (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type newIndexPath:(NSIndexPath *)newIndexPath { // Notify SwiftUI view about data changes [self.objectWillChange send]; } ``` However, when the data updates, it seems like the SwiftUI view is trying to access an object that has already been released, leading to the EXC_BAD_ACCESS error. I've also confirmed that the NSFetchedResultsController's delegate is still set correctly. I’ve verified that my managed object context is being passed correctly and holds strong references to the objects. Any insights on how I can debug this or avoid the EXC_BAD_ACCESS error would be a great help!