Handling NSManagedObjectContext Merging Conflicts in a Multi-threaded Objective-C App
I'm a bit lost with I'm trying to implement I'm working with an scenario with merging changes from different threads into my `NSManagedObjectContext`... My app is designed to allow users to edit objects in a background context while also updating the UI in the main thread. However, when trying to save changes made in a background context, I'm getting the following behavior: ``` The operation couldn’t be completed. (Cocoa behavior 133001.) ``` I've set up my Core Data stack using the `NSPersistentContainer`, and I'm using `performBlock:` to manage the background context. Here's a simplified version of what I'm doing: ```objc NSManagedObjectContext *backgroundContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType]; backgroundContext.parentContext = self.mainContext; [backgroundContext performBlock:^{ // Fetching an object to edit NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"EntityName"]; NSError *fetchError; NSArray *results = [backgroundContext executeFetchRequest:fetchRequest behavior:&fetchError]; if (!fetchError && results.count > 0) { NSManagedObject *objectToEdit = results[0]; [objectToEdit setValue:@"New Value" forKey:@"attributeName"]; // Modify the object NSError *saveError; if (![backgroundContext save:&saveError]) { NSLog(@"Failed to save background context: %@", saveError); } } else { NSLog(@"Fetch behavior: %@", fetchError); } }]; ``` The main context is being saved after changes are made in the background context using the parent context's `save:` method. However, I suspect that there might be a conflict when multiple edits are happening simultaneously, leading to this behavior. I tried using `mergeChangesFromContextDidSaveNotification:` to handle the merging but found that it's not always reliable when edits happen on multiple threads. Is there a recommended approach to manage these merging conflicts more gracefully? How can I ensure that changes from background contexts are appropriately merged into the main context without running into these errors? Any insights would be greatly appreciated! I'm working on a REST API that needs to handle this. Any examples would be super helpful. I've been using Objective-C for about a year now.