Using an @FetchRequest in my SwiftUI-redesigned app, I was looking to improve performance of my search and filtering on a List that has potentially a large amount of data. One of the things I was asking about was how to load some data initially and then fetch additional objects as the user scrolls. In a WWDC lab today, while viewing my code the Apple engineer noted I had set a .fetchLimit on my FetchRequest, and suggested that I should be setting a .fetchBatchSize. It sounded like that was designed to do exactly what I wanted. However, having attempted this, I can see from the console output that when I set a .fetchBatchSize of 50 and go to the view, it immediately loops through the entire collection of thousands of objects, attempting to load them into memory, and as some contain images this eventually crashes with an out of memory error. This data is presented in a List. Originally, inside that list there was a ForEach inside that list but the same problem was seen when I removed the ForEach and used: List(entries) { entry in if let entryData = viewModel.entryData(for: entry) { TimelineEntryView(entryData: entryData) } } Can you advise on what might be going on here? I recall that in the previous iteration of my app, in UIKit and using an NSFetchedResultsController I had the exact same symptom: setting a fetch batch size immediately traversed the whole collection in the datastore, leading to terrible performance rather than the hoped-for good performance. So I did not set a batch size then either. Am I holding this wrong? Is there something that might be triggering this?

In Core Data, you can use a pinned query generation to make sure that your app is working from a consistent view of the data store. If you have CloudKit sync turned on, and new changes come in that invalidate relationships, your app won't see them right away as long as it's looking at a pinned query generation. Since Swift Data doesn't yet support query generations, how do I deal with this issue in Swift Data apps? For example, let's say I have an address book app. I open a particular contact, and then tap a control on the screen that opens a list of images for that contact. While looking at the images, CloudKit sync retrieves changes made by other devices, which have completely removed the parent contact. How does my app know this has happened? Suppose the image browser screen needs to refer to the parent contact, or make changes to it, but the contact is no longer there because a background sync removed it.

Recently, I noticed many crashes reported daily for context.save() in my code. I tried to resolve the issue by refactoring some of the code. My key change is to use context.performAndWait to fetch Core Data objects instead of passing them around. I refactored the code to pass NSManagedObjectID around instead of NSManagedObject itself because NSManagedObjectID is thread-safe. However, even after the refactor, the issue is still. The crash log is attached as below. I'm confused that it doesn't crash on all devices so I have no clue to find the pattern of the crashes. I also enabled -com.apple.CoreData.ConcurrencyDebug 1 on my local dev box, but seems the error cannot be caught. The new code (after I refactored) still causes the crash: private func update(movements: [InferredMovement], from visitOutObjectId: NSManagedObjectID, to visitInObjectId: NSManagedObjectID?) { let context = PersistenceController.shared.container.viewContext context.performAndWait { guard let visitOut = try? context.existingObject(with: visitOutObjectId) as? Visit else { return } var visitIn: Visit? if let visitInObjectId { visitIn = try? context.existingObject(with: visitInObjectId) as? Visit } visitOut.movementsOut.forEach { context.delete($0) } visitIn?.movementsIn.forEach { context.delete($0) } for inferred in movements { let movement = Movement(context: context) movement.type = inferred.type movement.interval = inferred.interval movement.visitFrom_ = visitOut movement.visitTo_ = visitIn } visitOut.objectWillChange.send() context.saveIfNeeded() } } Note, saveIfNeeded() is an extension function implemented as: extension NSManagedObjectContext { /// Only performs a save if there are changes to commit. @discardableResult public func saveIfNeeded() -> Error? { guard hasChanges else { return nil } do { try save() return nil } catch { defaultLogger.error("Core Data Error: Failed to save context") return error } } } Crash context

I’m trying to sync data from the AppData on one device to another device with the same iCloud. It uploads the data to the CloudKit but it doesn’t write the data it fetches from the cloud into the AppData storage. It should store a timestamp, a few integers, and two lists of integers. The lists are both optional and store numbers. They can have 0 up to 50 numbers in them. This is the part where it should fetch the records and store them in the AppData let container = CKContainer(identifier: "iCloud.com.calchunt") let privateDatabase = container.privateCloudDatabase let dispatchGroup = DispatchGroup() var errors: [Error] = [] // Leere Liste zum Speichern neuer Spielsitzungen aus der Cloud var newGameSessions: [AppModule.GameSession] = [] for gameSession in gameSessions { let recordIDString = gameSession.id.uuidString // UUID zu String umwandeln let recordID = CKRecord.ID(recordName: recordIDString) dispatchGroup.enter() privateDatabase.fetch(withRecordID: recordID) { (existingRecord, error) in defer { dispatchGroup.leave() } if let error = error { // Fehler beim Abrufen des Records print("Fehler beim Abrufen des Records aus CloudKit: \(error.localizedDescription)") errors.append(error) } else if let existingRecord = existingRecord { // Record existiert in der Cloud print("Record mit ID \(existingRecord.recordID.recordName) existiert in CloudKit") // à berprüfen, ob der Record bereits im AppModule vorhanden ist if let _ = gameSessions.firstIndex(where: { $0.id == gameSession.id }) { // Record existiert bereits im AppModule, überspringe das Speichern print("Record mit ID \(existingRecord.recordID.recordName) existiert bereits im AppModule, überspringe das Speichern") } else { // Record existiert nicht im AppModule, füge ihn zur Liste der neuen Spielsitzungen hinzu let newGameSession = AppModule.GameSession( id: gameSession.id, losungszahl: gameSession.losungszahl, elapsedTime: gameSession.elapsedTime, currentDate: gameSession.currentDate, skipped: gameSession.skipped, skipped2: gameSession.skipped2, level: gameSession.level ) newGameSessions.append(newGameSession) print("Record mit ID \(existingRecord.recordID.recordName) wird zum AppModule hinzugefügt") } } else { // Record existiert nicht in der Cloud print("Record mit ID \(recordID.recordName) existiert nicht in CloudKit") } } } dispatchGroup.notify(queue: .main) { if !errors.isEmpty { for error in errors { print("Fehler beim Abrufen der Daten aus CloudKit: \(error.localizedDescription)") } } else { // Füge neue Spielsitzungen zum AppModule hinzu gameSessions.append(contentsOf: newGameSessions) // Speichere die aktualisierten Daten im AppStorage do { let encoder = JSONEncoder() let gameSessionsData = try encoder.encode(gameSessions) GameSessions = gameSessionsData print("Daten erfolgreich aus CloudKit geladen und im AppStorage gespeichert") } catch { print("Fehler beim Codieren und Speichern der Daten im AppStorage: \(error.localizedDescription)") } } } }

Hi, when setting up our Core Data stack in our iOS app (manually, with a NSManagedObjectModel/Context & NSPersistentStoreCoordinator) we have reports a rare bug we haven't been able to reproduce. Occasionally when adding a persistent store we get a NSCocoaErrorDomain 256 error (NSFileReadUnknownError) with NSSQLiteErrorDomain=4618 in the user info. That's SQLITE_IOERR_SHMOPEN , which the SQLite docs describe this way: I/O error within the xShmMap method on the sqlite3_io_methods object while trying to open a new shared memory segment It seems to specifically /not/ be a SQLITE_FULL error. Do you know what type of issue can cause this? Or where/how I can start tracking this down?

I have a large model. Not just large in complexity but literally there are gigabytes in the average user db. I want to enable saving data to this model from app extensions. However, I do not want to duplicate code or model setup. Is it recommended that I migrate to using a shared group model? How do you migrate existing stores to using shared containers? Or are there better ways to do it? For example, should I create a brand new store that uses a shared container? What are best practices?

For a bit of context, I store binary files of about 50KB in my Core Data. I noticed that enabling the "Allows External Storage" option doesn't seem to make any difference. Additionally, how does this setting work with CloudKit when using NSPersistentCloudKitContainer? Does this setting affect how the data is loaded into memory when accessed in Core Data in the app? Thank you very much!

Hi, I updated my iPad to iOS18 beta 1, and it seems to crash my app immediately, even though it's the App Store release version that's running fine on iOS17. The crash report points to some issue in NSManagedObjectContext performBlockAndWait: Thread 2 name: Dispatch queue: NSManagedObjectContext 0x303498000: CJCloudKitItemsUploaderQueue Thread 2 Crashed: 0 libsystem_kernel.dylib 0x1f1930254 __pthread_kill + 8 1 libsystem_pthread.dylib 0x2285fcef8 pthread_kill + 268 2 libsystem_c.dylib 0x1a9a76ad8 abort + 128 3 CJournal 0x105428818 0x104e28000 + 6293528 4 CJournal 0x1054261f4 0x104e28000 + 6283764 5 CoreFoundation 0x1a1c40a3c __handleUncaughtException + 660 6 libobjc.A.dylib 0x19eec8210 _objc_terminate() + 132 7 CJournal 0x1053f5ad0 0x104e28000 + 6085328 8 libc++abi.dylib 0x22852087c std::__terminate(void (*)()) + 16 9 libc++abi.dylib 0x228520820 std::terminate() + 108 10 libdispatch.dylib 0x1a99bd174 _dispatch_client_callout + 40 11 libdispatch.dylib 0x1a99cc7b8 _dispatch_lane_barrier_sync_invoke_and_complete + 56 12 CoreData 0x1a9c94a6c -[NSManagedObjectContext performBlockAndWait:] + 264 13 ContactsJournalDataKit 0x10643fb50 -[CJCloudKitModifyRecordsOperation createUnderlyingCKModifyRecordsOperationWithProcessList:withLimit:] + 408 14 ContactsJournalDataKit 0x10643f544 -[CJCloudKitModifyRecordsOperation main] + 848 15 Foundation 0x1a071e2e0 __NSOPERATION_IS_INVOKING_MAIN__ + 16 16 Foundation 0x1a071c530 -[NSOperation start] + 648 17 Foundation 0x1a07947a0 __NSOPERATIONQUEUE_IS_STARTING_AN_OPERATION__ + 16 18 Foundation 0x1a07943ec __NSOQSchedule_f + 172 19 libdispatch.dylib 0x1a99cc350 _dispatch_block_async_invoke2 + 148 20 libdispatch.dylib 0x1a99bd160 _dispatch_client_callout + 20 21 libdispatch.dylib 0x1a99c0610 _dispatch_continuation_pop + 596 22 libdispatch.dylib 0x1a99bfc40 _dispatch_async_redirect_invoke + 580 23 libdispatch.dylib 0x1a99cedf4 _dispatch_root_queue_drain + 392 24 libdispatch.dylib 0x1a99cf5f8 _dispatch_worker_thread2 + 156 25 libsystem_pthread.dylib 0x2285f9c40 _pthread_wqthread + 228 26 libsystem_pthread.dylib 0x2285f6488 start_wqthread + 8 Can anyone shed some light on this? I haven't rebuilt the app with Xcode 16 yet, just wanted to run the App Store version and see if it's compatible without doing anything.

I have been working on an ios application which I decided to use the new SwiftData architecture, and I now have realized that SwiftData does not support public or shared databases using SwiftData. I am a new and upcoming Swift developer, who has been self learning the Apple Swift technology. I just learned in this forum that Swift Data does not support Public and Shared Data and I also understand that no plans that have been announced to addressed this feature in the IOS 18 release time frame. The use case for my application is to implement a social type application, something like applications including X, facebook, etc. These type of applications appear to use Public, Shared and Private data in various existing Apple application. I would like to complete an application using Swift using ICloud, but I must assume that these current social applications are using other technologies. I am assuming you can do this in Core Data, but my understanding is Apple is asking that we use Swift Data to replace core data. I also am assuming that Swift data is built on core data technology layers. So ... to me it seems hopeful, somehow, to accomplish this using IOS 17 and follow the recommend Swift Data Path. What are my options for completing these data objectives in IOS? I hope I am addressing these questions in the proper and best forum? Much thanks for any suggestions.

i have received a lot of crash log only in iOS16 the crash occured when i called : [[PHImageManager defaultManager] requestImageDataForAsset:asset options:options resultHandler:resultHandler] here is the crash log Exception Type: NSInternalInconsistencyException ExtraInfo: Code Type: arm64 OS Version: iPhone OS 16.0 (20A5328h) Hardware Model: iPhone14,3 Launch Time: 2022-07-30 18:43:25 Date/Time: 2022-07-30 18:49:17 *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason:Unhandled error (NSCocoaErrorDomain, 134093) occurred during faulting and was thrown: Error Domain=NSCocoaErrorDomain Code=134093 "(null)" Last Exception Backtrace: 0 CoreFoundation 0x00000001cf985dc4 0x1cf97c000 + 40388 1 libobjc.A.dylib 0x00000001c8ddfa68 0x1c8dc8000 + 96872 2 CoreData 0x00000001d56d2358 0x1d56cc000 + 25432 3 CoreData 0x00000001d56fa19c 0x1d56cc000 + 188828 4 CoreData 0x00000001d5755be4 0x1d56cc000 + 564196 5 CoreData 0x00000001d57b0508 0x1d56cc000 + 935176 6 PhotoLibraryServices 0x00000001df1783e0 0x1df0ed000 + 570336 7 Photos 0x00000001df8aa88c 0x1df85d000 + 317580 8 PhotoLibraryServices 0x00000001df291de0 0x1df0ed000 + 1723872 9 CoreData 0x00000001d574e518 0x1d56cc000 + 533784 10 libdispatch.dylib 0x00000001d51fc0fc 0x1d51f8000 + 16636 11 libdispatch.dylib 0x00000001d520b634 0x1d51f8000 + 79412 12 CoreData 0x00000001d574e0a0 0x1d56cc000 + 532640 13 PhotoLibraryServices 0x00000001df291d94 0x1df0ed000 + 1723796 14 PhotoLibraryServices 0x00000001df291434 0x1df0ed000 + 1721396 15 Photos 0x00000001df8a8380 0x1df85d000 + 308096 16 Photos 0x00000001df89d050 0x1df85d000 + 262224 17 Photos 0x00000001df87f62c 0x1df85d000 + 140844 18 Photos 0x00000001df87ee94 0x1df85d000 + 138900 19 Photos 0x00000001df87e594 0x1df85d000 + 136596 20 Photos 0x00000001df86b5c8 0x1df85d000 + 58824 21 Photos 0x00000001df86d938 0x1df85d000 + 67896 22 Photos 0x00000001dfa37a64 0x1df85d000 + 1944164 23 Photos 0x00000001dfa37d18 0x1df85d000 + 1944856 24 youavideo -[YouaImageManager requestImageDataForAsset:options:resultHandler:] (in youavideo) (YouaImageManager.m:0) 27 25 youavideo -[YouaAlbumTransDataController requstTransImageHandler:] (in youavideo) (YouaAlbumTransDataController.m:0) 27 26 youavideo -[YouaAlbumTransDataController requstTransWithHandler:] (in youavideo) (YouaAlbumTransDataController.m:77) 11 27 youavideo -[YouaUploadTransDataOperation startTrans] (in youavideo) (YouaUploadTransDataOperation.m:102) 19 28 Foundation 0x00000001c9e78038 0x1c9e3c000 + 245816 29 Foundation 0x00000001c9e7d704 0x1c9e3c000 + 268036 30 libdispatch.dylib 0x00000001d51fa5d4 0x1d51f8000 + 9684 31 libdispatch.dylib 0x00000001d51fc0fc 0x1d51f8000 + 16636 32 libdispatch.dylib 0x00000001d51ff58c 0x1d51f8000 + 30092 33 libdispatch.dylib 0x00000001d51febf4 0x1d51f8000 + 27636 34 libdispatch.dylib 0x00000001d520db2c 0x1d51f8000 + 88876 35 libdispatch.dylib 0x00000001d520e338 0x1d51f8000 + 90936 36 libsystem_pthread.dylib 0x00000002544b9dbc 0x2544b9000 + 3516 37 libsystem_pthread.dylib 0x00000002544b9b98 0x2544b9000 + 2968 i can't find the error code 134093 definition i don't know what's going wrong in iOS16 Would anyone have a hint of why this could happen and how to resolve it? thanks very much

I have an app that uses CoreData and I want to migrate to SwiftData. After following the Migrate to SwiftData session, I only need to point to my old Core Data file to read the old data and convert it to the new SwiftData format. My question is how do I do this? Maybe worth mentioning is that my NSPersistentContainer(name: "Model") is different to my app name. Possible Solution? According to a Tweet by Donny Wals this is done this way: By default a SwiftData ModelContainer will create its underlying storage in a file called default.store. If you want to change this so you can use an existing Core Data SQLite file, you can point your container to that file instead: // point to your old sqlite file let url = URL.applicationSupportDirectory.appending(path: "Model.sqlite") let config = ModelConfiguration(url: url) modelContainer = try ModelContainer(for: [ Movie.self ], config) My Tested Code @main struct SwiftData_TestApp: App { let url = URL.applicationSupportDirectory.appending(path: "Model.sqlite") let config = ModelConfiguration(url: url) let modelContainer = try ModelContainer(for: [ Item.self ], config) var body: some Scene { WindowGroup { ContentView() } .modelContainer(modelContainer) } } The problem here is that I don’t get it to work in the main app struct. When using this the way described in Dive deeper into SwiftData (at 6:58) I only get the error: Cannot use instance member 'url' within property initializer; property initializers run before 'self' is available PS: There seems to be an issue with this WWDC session method anyway – see this post.

I have a native SwiftUI Mac app which is based off my iOS app and includes Core Data with iCloud sync. As per my understanding, when a user makes a change on one of the devices a remote notification is sent to the others. I have a widget which displays information from Core Data and the remote notification makes the widget update its information on the next timeline refresh without the user having to open the app manually. My question is, if an app is closed on macOS so it's not even running in the Dock, do remote notifications work? This page says "the delegate receives this message when the application is running and a remote notification arrives for it". Does that mean the app won't receive remote CloudKit notifications when closed on macOS?

Hi, does someone knows about the bug, that the NSPersistentCloudKitContainer doesn't return CKShares at the first time? Is this an intended behavior? My current fix: let container: NSPersistentCloudKitContainer = .... // Fix begin let managedObject = .... // Object which is in a share let record = container.record(for: managedObject.objectID) // Fix end let shares = (try? container.fetchShares(in: nil)) ?? [] If I execute exactly the same code without the fix that I fetch the record first, then it returns 0 shares. With the fix it is currently 9 shares (the actual count of the shares). Another fix: let container: NSPersistentCloudKitContainer = .... // Fix begin let _ = try? container.fetchShares(in: nil) Thread.sleep(forTimeInterval: 0.1) // Fix end let shares = (try? container.fetchShares(in: nil)) ?? [] For that fix it also returns at the second time the expected count of shares. But without the delay it returns also at the second time zero shares. Anyone had the same problem and if so, how do you solve it correctly? Thanks!

We started to see some crashes in our iOS app a few seconds after launch with the following reason: Exception Type: EXC_CRASH (SIGILL) Exception Codes: 0x0000000000000000, 0x0000000000000000 Termination Reason: SIGNAL 4 Illegal instruction: 4 when calling [NSPersistentContainer loadPersistentStoresWithCompletionHandler:]. I've looked through Understanding the exception types in a crash report page, but couldn't find this type there. Any ideas what could it be?

I recently converted a Core Data app to use CloudKit. Before the conversion, the sqlite file was around 25MB. After the conversion, the file grew to over one gigabyte. I ran sqlite3_analyzer on the new file and found that a single table, ANSCKRECORDMETADATA, used 95% of the storage, 998MB. Is this to be expected? I confess that the conversion was a bit bumpy. Maybe I did something to create a monstrosity. If not expected, should I revert to the old Core Data file, create a new CloudKit container, and repeat the conversion.

My app uses Core Data to store an synchronise the data. It runs on iOS, iPadOS and now WatchOS. The records are stored in the private and shared CloudKit database. Running the app in developer mode, syncing is fine for all devices. But as soon as I switch to production mode using TestFlight, the Watch only syncs the data of the shared records, while iPad and iPhone still are syncing all records (private and shared) correctly. I run out of ideas where to search for the reason of this problem. I use one module to setup the persistent store for iOS, iPadOs and WatchOS. Any ideas are well come.

Hi, I have been working on some kind of network filtering app for iOS using Content Filter Provider. And I have stored rules for each domain. As of right now, I use UserDefaults with my app's bundle suite to store and observe rules. I have also read this documentation page for UserDefaults link. Is it okay to use UserDefaults in my case, if I have rules added/modified dynamically as the flow is intercepted, or should I pick some other approach like Core Data, SwiftData, etc.? Thank you!

SwiftData includes support for CloudKit sync. However, I don't see any way to add conflict resolution behavior. For example, if different devices set different values for a field, or if a relationship is orphaned because of a deletion on another device, the application has to handle this somehow. In Core Data (which SwiftData wraps), you can handle this with the conflict resolution system (docs) and classes like NSMergePolicy. Is any of this accessible in SwiftData? If not, how do you deal with conflicts when syncing a SwiftData model with the cloud?

Has anyone successfully persisted Color, particularly in SwiftData? So far my attempts have failed: Making Color conform to Codable results in a run time error (from memory something about ColorBox). Color.Resolved already conforms Codable but this results in "SwiftData/ModelCoders.swift:124: Fatal error: Composite Coder only supports Keyed Container" None of the other color types conform to Codable (CGColor, NSColor and UIColor) so does the swift language really not have a persistable color type?

Recently, I have made quite extensive changes to my schema and need to migrate my CoreData + CloudKit model to a new version. The changes require me to use a custom NSEntityMigrationPolicy because I have a rather complex mapping between some old entities and new entities. I have added a new model version. Deleted some entities, and added some entities. I have defined the NSEntityMigrationPolicy with createDestinationInstances(forSource:in:manager:) and createRelationships(forDestination:in:manager:). I have created a new Core Data Mapping Model. This was probably unnecessary. Within the Core Data Mapping Model, I have specified Custom Policy for all entities. In my container setup, I added two options, as below: storeDescription.setOption(false as NSNumber, forKey: NSMigratePersistentStoresAutomaticallyOption) storeDescription.setOption(false as NSNumber, forKey: NSInferMappingModelAutomaticallyOption) I mostly followed a "Core Data Heavyweight Migration" guide. I'm unable to share the link, but it can be quite easily found on the web. (It's not for CloudKit specifically.) When I run my app, I am getting the most basic of errors, which is: The managed object model version used to open the persistent store is incompatible with the one that was used to create the persistent store. So I guess that migration wasn't even attempted, which makes sense because I set NSMigratePersistentStoresAutomaticallyOption to false. I tried to go beyond what I could find on the web and attempted to manually initialize migration: let sourceModel = container.persistentStoreCoordinator.managedObjectModel guard let modelURL = Bundle.main.url(forResource: "MyModelName", withExtension: "xcdatamodeld") else { fatalError("Unable to locate model file.") } guard let destinationModel = NSManagedObjectModel(contentsOf: modelURL) else { fatalError("Unable to load destination model.") } let migrationManager = NSMigrationManager(sourceModel: sourceModel, destinationModel: destinationModel) let mappingModel = NSMappingModel(from: [Bundle.main], forSourceModel: sourceModel, destinationModel: destinationModel)! migrationManager.currentEntityMapping.entityMigrationPolicyClassName = "MyMigrationPolicyClassName" I am then stuck at the migrateStore(from:type:mapping:to:type:) method. It seems to target only local storage, not CloudKit. Otherwise, what do I provide for URLs and types? Any guidance for custom logic CoreData with CloudKit migration would be greatly appreciated.