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SwiftData serious bug with relationships and CloudKit in iOS 18.0 (Xcode 16 Beta)
Hi guys. Can someone please confirm this bug so I report it? The issue is that SwiftData relationships don't update the views in some specific situations on devices running iOS 18 Beta. One clear example is with CloudKit. I created a small example for testing. The following code creates two @models, one to store bands and another to store their records. The following code works with no issues. (You need to connect to a CloudKit container and test it on two devices) import SwiftUI import SwiftData struct ContentView: View { @Environment(\.modelContext) private var modelContext @Query private var records: [Record] var body: some View { NavigationStack { List(records) { record in VStack(alignment: .leading) { Text(record.title) Text(record.band?.name ?? "Undefined") } } .toolbar { ToolbarItem { Button("Add Record") { let randomNumber = Int.random(in: 1...100) let newBand = Band(name: "New Band \(randomNumber)", records: nil) modelContext.insert(newBand) let newRecord = Record(title: "New Record \(randomNumber)", band: newBand) modelContext.insert(newRecord) } } } } } } @Model final class Record { var title: String = "" var band: Band? init(title: String, band: Band?) { self.title = title self.band = band } } @Model final class Band { var name: String = "" var records: [Record]? init(name: String, records: [Record]?) { self.name = name self.records = records } } This view includes a button at the top to add a new record associated with a new band. The data appears on both devices, but if you include more views inside the List, the views on the second device are not updated to show the values of the relationships. For example, if you extract the row to a separate view, the second device shows the relationships as "Undefined". You can try the following code. struct ContentView: View { @Environment(\.modelContext) private var modelContext @Query private var records: [Record] var body: some View { NavigationStack { List { ForEach(records) { record in RecordRow(record: record) } } .toolbar { ToolbarItem { Button("Add Record") { let randomNumber = Int.random(in: 1...100) let newBand = Band(name: "New Band \(randomNumber)", records: nil) modelContext.insert(newBand) let newRecord = Record(title: "New Record \(randomNumber)", band: newBand) modelContext.insert(newRecord) } } } } } } struct RecordRow: View { let record: Record var body: some View { VStack(alignment: .leading) { Text(record.title) Text(record.band?.name ?? "Undefined") } } } Here I use a ForEach loop and move the row to a separate view. Now on the second device the relationships are nil, so the row shows the text "Undefined" instead of the name of the band. I attached an image from my iPad. I inserted all the information on my iPhone. The first three rows were inserted with the first view. But the last two rows were inserted after I extracted the rows to a separate view. Here you can see that the relationships are nil and therefore shown as "Undefined". The views are not updated to show the real value of the relationship. This example shows the issue with CloudKit, but this also happens locally in some situations. The system doesn't detect updates in relationships and therefore doesn't refresh the views. Please, let me know if you can reproduce the issue. I'm using Mac Sequoia 15.1, and two devices with iOS 18.0.
3
0
829
Apr ’25
SwiftData: Crash when deleting from model, but only in prod
I'm testing my app before releasing to testers, and my app (both macOS and iOS) is crashing when I perform one operation, but only in the production build. I have data that loads from a remote source, and can be periodically updated. There is an option to delete all of that data from the iCloud data store, unless the user has modified a record. Each table has a flag to indicate that (userEdited). Here's the function that is crashing: func deleteCommonData<T:PersistentModel & SDBuddyModel>(_ type: T.Type) throws { try modelContext.delete(model: T.self, where: #Predicate<T> { !$0.userEdited }) } Here's one of the calls that results in a crash: try modelManager.deleteCommonData(Link.self) Here's the error from iOS Console: SwiftData/DataUtilities.swift:85: Fatal error: Couldn't find \Link.<computed 0x0000000104b9d208 (Bool)> on Link with fields [SwiftData.Schema.PropertyMetadata(name: "id", keypath: \Link.<computed 0x0000000104b09b44 (String)>, defaultValue: Optional("54EC6602-CA7C-4EC7-AC06-16E7F2E22DE7"), metadata: nil), SwiftData.Schema.PropertyMetadata(name: "name", keypath: \Link.<computed 0x0000000104b09b84 (String)>, defaultValue: Optional(""), metadata: nil), SwiftData.Schema.PropertyMetadata(name: "url", keypath: \Link.<computed 0x0000000104b09bc4 (String)>, defaultValue: Optional(""), metadata: nil), SwiftData.Schema.PropertyMetadata(name: "desc", keypath: \Link.<computed 0x0000000104b09c04 (String)>, defaultValue: Optional(""), metadata: nil), SwiftData.Schema.PropertyMetadata(name: "userEdited", keypath: \Link.<computed 0x0000000104b09664 (Bool)>, defaultValue: Optional(false), metadata: nil), SwiftData.Schema.PropertyMetadata(name: "modified", keypath: \Link.<computed 0x0000000104b09c44 (Date)>, defaultVal<…> Here's a fragment of the crash log: Exception Type: EXC_BREAKPOINT (SIGTRAP) Exception Codes: 0x0000000000000001, 0x000000019373222c Termination Reason: Namespace SIGNAL, Code 5, Trace/BPT trap: 5 Terminating Process: exc handler [80543] Thread 0 Crashed: 0 libswiftCore.dylib 0x19373222c _assertionFailure(_:_:file:line:flags:) + 176 1 SwiftData 0x22a222160 0x22a1ad000 + 479584 2 SwiftData 0x22a2709c0 0x22a1ad000 + 801216 3 SwiftData 0x22a221b08 0x22a1ad000 + 477960 4 SwiftData 0x22a27b0ec 0x22a1ad000 + 844012 5 SwiftData 0x22a27b084 0x22a1ad000 + 843908 6 SwiftData 0x22a28182c 0x22a1ad000 + 870444 7 SwiftData 0x22a2809e8 0x22a1ad000 + 866792 8 SwiftData 0x22a285204 0x22a1ad000 + 885252 9 SwiftData 0x22a281c7c 0x22a1ad000 + 871548 10 SwiftData 0x22a27cf6c 0x22a1ad000 + 851820 11 SwiftData 0x22a27cc48 0x22a1ad000 + 851016 12 SwiftData 0x22a27a6b0 0x22a1ad000 + 841392 13 SwiftData 0x22a285b2c 0x22a1ad000 + 887596 14 SwiftData 0x22a285a10 0x22a1ad000 + 887312 15 SwiftData 0x22a285bcc 0x22a1ad000 + 887756 16 SwiftData 0x22a27cf6c 0x22a1ad000 + 851820 17 SwiftData 0x22a27cc48 0x22a1ad000 + 851016 18 SwiftData 0x22a27a6b0 0x22a1ad000 + 841392 19 SwiftData 0x22a27c0d8 0x22a1ad000 + 848088 20 SwiftData 0x22a27a654 0x22a1ad000 + 841300 21 SwiftData 0x22a1be548 0x22a1ad000 + 70984 22 SwiftData 0x22a1cfd64 0x22a1ad000 + 142692 23 SwiftData 0x22a1b9618 0x22a1ad000 + 50712 24 SwiftData 0x22a1d2e8c 0x22a1ad000 + 155276 25 CoreData 0x187fbb568 thunk for @callee_guaranteed () -> (@out A, @error @owned Error) + 28 26 CoreData 0x187fc2300 partial apply for thunk for @callee_guaranteed () -> (@out A, @error @owned Error) + 24 27 CoreData 0x187fc19c4 closure #1 in closure #1 in NSManagedObjectContext._rethrowsHelper_performAndWait<A>(fn:execute:rescue:) + 192 28 CoreData 0x187fbbda8 thunk for @callee_guaranteed @Sendable () -> () + 28 29 CoreData 0x187fbbdd0 thunk for @escaping @callee_guaranteed @Sendable () -> () + 28 30 CoreData 0x187f663fc developerSubmittedBlockToNSManagedObjectContextPerform + 252 31 libdispatch.dylib 0x180336ac4 _dispatch_client_callout + 16 32 libdispatch.dylib 0x18032c940 _dispatch_lane_barrier_sync_invoke_and_complete + 56 33 CoreData 0x187fd7290 -[NSManagedObjectContext performBlockAndWait:] + 364 34 CoreData 0x187fc1fb8 NSManagedObjectContext.performAndWait<A>(_:) + 544 35 SwiftData 0x22a1b877c 0x22a1ad000 + 46972 36 SwiftData 0x22a1be2a8 0x22a1ad000 + 70312 37 SwiftData 0x22a1c0e34 0x22a1ad000 + 81460 38 SwiftData 0x22a23ea94 0x22a1ad000 + 596628 39 SwiftData 0x22a256828 0x22a1ad000 + 694312 40 Sourdough Buddy 0x104e5dc98 specialized ModelManager.deleteCommonData<A>(_:) + 144 (ModelManager.swift:128) [inlined] 41 Sourdough Buddy 0x104e5dc98 closure #1 in SettingsView.clearStarterData.getter + 876 (SettingsView.swift:243) It works if I do the following instead: try modelContext.delete(model: Link.self, where: #Predicate { !$0.userEdited }) Why would the func call work in development, but crash in production? And why does doing the more verbose way work instead? I think this is a bug. Thanks
3
1
103
Oct ’25
Strange behavior with 100k+ records in NSPersistentCloudKitContainer
I have been using the basic NSPersistentContainer with 100k+ records for a while now with no issues. The database size can fluctuate a bit but on average it takes up about 22mb on device. When I switch the container to NSPersistentCloudKitContainer, I see a massive increase in size to ~150mb initially. As the sync engine uploads records to iCloud it has ballooned to over 600mb on device. On top of that, the user's iCloud usage in settings reports that it takes up 1.7gb in the cloud. I understand new tables are added and history tracking is enabled but the size increase seems a bit drastic. I'm not sure how we got from 22mb to 1.7gb with the exact same data. A few other things that are important to note: I import all the 100k+ records at once when testing the different containers. At the time of the initial import there is only 1 relation (an import group record) that all the records are attached to. I save the background context only once after all the records and the import group have been made and added to the context. After the initial import, some of these records may have a few new relations added to them over time. I suppose this could be causing some of the size increase, but its only about 20,000 records that are updated. None of the records include files/ large binary data. Most of the attributes are encrypted. I'm syncing to the dev iCloud environment. When I do make a change to a single attribute in a record, CloudKit reports that every attribute has been modified (not sure if this is normal or not ) Also, When syncing to a new device, the sync can take hours - days. I'm guessing it's having to sync both the new records and the changes, but it exponentially gets slower as more records are downloaded. The console will show syncing activity, but new records are being added at a slower rate as more records are added. After about 50k records, it grinds to a halt and while the console still shows sync activity, only about 100 records are added every hour. All this to say i'm very confused where these issues are coming from. I'm sure its a combination of how i've setup my code and the vast record count, record history, etc. If anyone has any ideas it would be much appreciated.
3
1
662
Nov ’25
Debugging help
No matter what I do, I keep getting the error Thread 1: EXC_BREAKPOINT (code=1, subcode=0x2648fc364) for the line: transactions = try modelContext.fetch(descriptor) in the code below. My app opens, but freezes on the home page and I can't click anything. I am not sure how to fix initialization issues. I am creating a financial assistant app that connects plaid and opoenai api. var descriptor = FetchDescriptor&lt;ExpenseTransaction&gt;() descriptor.sortBy = [SortDescriptor(\.date, order: .reverse)] descriptor.fetchLimit = 200 transactions = try modelContext.fetch(descriptor) print("Successfully loaded \(transactions.count) transactions") } catch { print("Error in loadLocalTransactions: \(error)") transactions = [] } }
3
0
85
Apr ’25
Core Data Light Migration Crash When Widget is Installed (Error 134100)
I'm experiencing a crash during a lightweight Core Data migration when a widget that accesses the same database is installed. The migration fails with the following error: CoreData: error: addPersistentStoreWithType:configuration:URL:options:error: returned error NSCocoaErrorDomain (134100) error: userInfo: CoreData: error: userInfo: error: metadata : { NSPersistenceFrameworkVersion = 1414; NSStoreModelVersionChecksumKey = "dY78fBnnOm7gYtb+QT14GVGuEmVlvFSYrb9lWAOMCTs="; NSStoreModelVersionHashes = { Entity1 = { ... }; Entity2 = { ... }; Entity3 = { ... }; Entity4 = { ... }; Entity5 = { ... }; }; NSStoreModelVersionHashesDigest = "aOalpc6zSzr/VpduXuWLT8MLQFxSY4kHlBo/nuX0TVQ/EZ+MJ8ye76KYeSfmZStM38VkyeyiIPf4XHQTMZiH5g=="; NSStoreModelVersionHashesVersion = 3; NSStoreModelVersionIdentifiers = ( "" ); NSStoreType = SQLite; NSStoreUUID = "9AAA7AB7-18D4-4DE4-9B54-893D08FA7FC4"; "_NSAutoVacuumLevel" = 2; } The issue occurs only when the widget is installed. If I remove the widget’s access to the Core Data store, the migration completes successfully. The crash happens only once—after the app is restarted, everything works fine. This occurs even though I'm using lightweight migration, which should not require manual intervention. My suspicion is that simultaneous access to the Core Data store by both the main app and the widget during migration might be causing the issue. Has anyone encountered a similar issue? Is there a recommended way to ensure safe migration while still allowing the widget to access Core Data? Any insights or recommendations would be greatly appreciated.
3
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712
Feb ’25
SwiftData: Unexpected backing data for snapshot creation
When deleting a SwiftData entity, I sometimes encounter the following error in a document based SwiftUI app: Fatal error: Unexpected backing data for snapshot creation: SwiftData._FullFutureBackingData<MyEntityClass> The deletion happens in a SwiftUI View and the code used to retrieve the entity is standard (the ModelContext is injected from the @Environment): let myEntity = modelContext.model(for: entityIdToDelete) modelContext.delete(myEntity) Unfortunately, I haven't yet managed to isolate this any further in order to come up with a reproducible PoC. Could you give me further information about what this error means?
3
0
216
Oct ’25
Accessing "iCloud Drive" folder in Files on iPhone from App written in Swift
I am trying to read and write a text file from an App written in Swift in XCode directly to the "iCloud Drive" folder in Files on the iPhone. The app worked readlly reading and writing to the Documents folder in the App container, and then readily to the "On My iPhone" folder in Files after adding 2 lines to the plist that I found in a search online. But I have been unable to get to the iCloud Drive folder. I found an item called "Enabling Document Storage in iCloud Drive" in "iCloud Design Guide" with additional plist entries that states "These settings allow iCloud Drive to provide public access to the files stored in your app’s container": NSUbiquitousContainers iCloud.com.example.MyApp NSUbiquitousContainerIsDocumentScopePublic NSUbiquitousContainerSupportedFolderLevels Any NSUbiquitousContainerName MyApp I think I changed the MyApp items appropriately. I have enabled iCloud in my App and the XCode General, and Signing entries. But this does not work. There are no error messages and no "Steps" shown in the "Capabilities" entry in Xcode. A little help? :-)
3
0
1.2k
Jan ’25
Documents folder of my app not shown in iCloud Drive in Finder
The problem is that the iCloud Drive directory of my app does not appear in my iCloud Drive in Finder despite the (I think) correct settings in my info.plist file (see below). In Terminal, I can see the folder and it also contains .txt files. What can I do to make the folder visible in Finder and the Files app? <key>NSUbiquitousContainers</key> <dict> <key>iCloud.vmk.NewsSwiper</key> <dict> <key>NSUbiquitousContainerIsDocumentScopePublic</key> <true/> <key>NSUbiquitousContainerName</key> <string>RSS-Filter</string> <key>NSUbiquitousContainerIdentifier</key> <string>iCloud.vmk.NewsSwiper</string> <key>NSUbiquitousContainerSupportedFolderLevels</key> <string>Any</string> </dict> </dict>
3
0
754
Feb ’25
NSFileVersion.currentVersionOfItem not consistent across devices after simultaneous edit
I’m building an app that edits files in iCloud and uses an NSFilePresenter to monitor changes. When a conflict occurs, the system calls presentedItemDidGain(_:). In that method, I merge the versions by reading the current (canonical) version using NSFileVersion.currentVersionOfItem(at:) and the conflicting ones using NSFileVersion.unresolvedConflictVersionsOfItem(at:). This generally works, but sometimes, if two devices edit the same file at the same time, each device sees its own local version as the current one. For example: Device A writes fileVerA (slightly later in real time) Device B writes fileVerB On Device A all works fine, currentVersionOfItem returns fileVerA, as expected, and unresolvedConflictVersionsOfItem returns [fileVerB]. But on Device B, currentVersionOfItem returns fileVerB!? And unresolvedConflictVersionsOfItem returns the same, local file [fileVerB], without any hint of the other conflicting version, fileVerA. Later, the newer version from the Device A arrives on Device B as a normal, non-conflicting update via presentedItemDidChange(_:). This seems to contradict Apple’s documentation: “The currentVersionOfItemAtURL: method returns an NSFileVersion object representing what’s referred to as the current file; the current file is chosen by iCloud on some basis as the current “conflict winner” and is the same across all devices.” Is this expected behavior, or a bug in how iCloud reports file versions?
3
0
188
Oct ’25
Mac App Crashing with Illegal Instructions
I have made a Swift App for MacOS 15 under XCode 16.3, which runs fine. I also want to run it under the previous MacOS 14. Unfortunately it crashes without even starting up (it does not even reach the first log output statement on the first view) The crash reason is Crashed Thread: 0 Dispatch queue: com.apple.main-thread Exception Type: EXC_BAD_INSTRUCTION (SIGILL) Exception Codes: 0x0000000000000001, 0x0000000000000000 Termination Reason: Namespace SIGNAL, Code 4 Illegal instruction: 4 Terminating Process: exc handler [2970] I have set the miminium deployment to MacOS 14.0 but to no effect. The XCode machine is a MacOS 15.4 on Arm M3 and the target machine is MacOS 14.7.5 on Intel (MacBook Air) I think it might be related to the compiler and linker settings.
3
0
82
Apr ’25
SwiftData + CKSyncEngine
Hi, I'm building a habit tracking app for iOS and macOS. I want to use up to date technologies, so I'm using SwiftUI and SwiftData. I want to store user data locally on device and also sync data between device and iCloud server so that the user could use the app conveniently on multiple devices (iPhone, iPad, Mac). I already tried SwiftData + NSPersistentCloudKitContainer, but I need to control when to sync data, which I can't control with NSPersistentCloudKitContainer. For example, I want to upload data to server right after data is saved locally and download data from server on every app open, on pull-to-refresh etc. I also need to monitor sync progress, so I can update the UI and run code based on the progress. For example, when downloading data from server to device is in progress, show "Loading..." UI, and when downloading finishes, I want to run some app business logic code and update UI. So I'm considering switching from NSPersistentCloudKitContainer to CKSyncEngine, because it seems that with CKSyncEngine I can control when to upload and download data and also monitor the progress. My database schema (image below) has relationships - "1 to many" and "many to many" - so it's convenient to use SwiftData (and underlying CoreData). Development environment: Xcode 16.1, macOS 15.1.1 Run-time configuration: iOS 18.1.1, macOS 15.1.1 My questions: 1-Is it possible to use SwiftData for local data storage and CKSyncEngine to sync this local data storage with iCloud? 2-If yes, is there any example code to implement this? I've been studying the "CloudKit Samples: CKSyncEngine" demo app (https://github.com/apple/sample-cloudkit-sync-engine), but it uses a very primitive approach to local data storage by saving data to a JSON file on disk. It would be very helpful to have the same demo app with SwiftData implementation! 3-Also, to make sure I don't run into problems later - is it okay to fire data upload (sendChanges) and download (fetchChanges) manually with CKSyncEngine and do it often? Are there any limits how often these functions can be called to not get "blocked" by the server? 4-If it's not possible to use SwiftData for local data storage and CKSyncEngine to sync this local data storage with iCloud, then what to use for local storage instead of SwiftData to sync it with iCloud using CKSyncEngine? Maybe use SwiftData with the new DataStore protocol instead of the underlying CoreData? All information highly appreciated! Thanks, Martin
3
0
1.4k
Dec ’24
SwiftData and CloudKit Development vs. Production Database
Hi, I'm working on a macOS app that utilizes SwiftData to save some user generated content to their private databases. It is not clear to me at which point the app I made starts using the production database. I assumed that if I produce a Release build that it will be using the prod db, but that doesn't seem to be the case. I made the mistake of distributing my app to users before "going to prod" with CloudKit. So after I realized what I had done, I inspected my CloudKit dashboard and records and I found the following: For my personal developer account the data is saved in the Developer database correctly and I can inspect it. When I use the "Act as iCloud account" feature and use one of my other accounts to inspect the data, I notice that for the other user, the data is neither in the Development environment nor the Production environment. Which leads me to believe it is only stored locally on that user's machine, since the app does in fact work, it's just not syncing with other devices of the same user. So, my question is: how do I "deploy to production"? I know that there is a Deploy Schema Changes button in the CloudKit dashboard. At which point should I press that? If I press it now, before distributing a new version of my app, will that somehow "signal" the already running apps on user's machines to start using the Production database? Is there a setting in Xcode that I need to check for my Release build, so that the app does in fact start using the production db? Is there a way to detect in the code whether the app is using the Production database or not? It would be useful so I can write appropriate migration logic, since I don't want to loose existing data users already have saved locally.
3
0
1.3k
Jan ’25
Core Data + CKSyncEngine with Swift 6 — concurrency, Sendable, and best practices validation
Hi everyone, I’ve been working on migrating my app (SwimTimes, which helps swimmers track their times) to use Core Data + CKSyncEngine with Swift 6. After many iterations, forum searches, and experimentation, I’ve created a focused sample project that demonstrates the architecture I’m using. The good news: 👉 I believe the crashes I was experiencing are now solved, and the sync behavior is working correctly. 👉 The demo project compiles and runs cleanly with Swift 6. However, before adopting this as the final architecture, I’d like to ask the community (and hopefully Apple engineers) to validate a few critical points, especially regarding Swift 6 concurrency and Core Data contexts. Architecture Overview Persistence layer: Persistence.swift sets up the Core Data stack with a main viewContext and a background context for CKSyncEngine. Repositories: All Core Data access is abstracted into repository classes (UsersRepository, SwimTimesRepository), with async/await methods. SyncEngine: Wraps CKSyncEngine, handles system fields, sync tokens, and bridging between Core Data entities and CloudKit records. ViewModels: Marked @MainActor, exposing @Published arrays for SwiftUI. They never touch Core Data directly, only via repositories. UI: Simple SwiftUI views bound to the ViewModels. Entities: UserEntity → represents swimmers. SwimTimeEntity → times linked to a user (1-to-many). Current Status The project works and syncs across devices. But there are two open concerns I’d like validated: Concurrency & Memory Safety Am I correctly separating viewContext (main/UI) vs. background context (used by CKSyncEngine)? Could there still be hidden risks of race conditions or memory crashes that I’m not catching? Swift 6 Sendable Compliance Currently, I still need @unchecked Sendable in the SyncEngine and repository layers. What is the recommended way to fully remove these workarounds and make the code safe under Swift 6’s stricter concurrency rules? Request Please review this sample project and confirm whether the concurrency model is correct. Suggest how I can remove the @unchecked Sendable annotations safely. Any additional code improvements or best practices would also be very welcome — the intention is to share this as a community resource. I believe once finalized, this could serve as a good reference demo for Core Data + CKSyncEngine + Swift 6, helping others migrate safely. Environment iOS 18.5 Xcode 16.4 macOS 15.6 Swift 6 Sample Project Here is the full sample project on GitHub: 👉 [https://github.com/jarnaez728/coredata-cksyncengine-swift6] Thanks a lot for your time and for any insights! Best regards, Javier Arnáez de Pedro
3
0
437
Sep ’25
CloudKit and SwiftData not syncing on MacOS
I have a simple app that uses SwiftUI and SwiftData to maintain a database. The app runs on multiple iPhones and iPads and correctly synchronises across those platforms. So I am correct setting Background Modes and Remote Notifications. I have also correctly setup my Model Configuration and ModelContainer (Otherwise I would expect syncing to fail completely). The problem arises when I run on a Mac (M1 or M3) either using Mac Designed for iPad or Mac Catalyst. This can be debugging in Xcode or running the built app. Then the app does not reflect changes made in the iPhone or iPad apps unless I follow a specific sequence. Leave the app, (e.g click on a Finder window), then come back to the app (i.e click on the app again). Now the app will show the changes made on the iPhone/iPad. It looks like the app on the Mac is not processing remote notifications when in the background - it only performs them when the app has just become active. It also looks like the Mac is not performing these sync operations when the app is active. I have tried waiting 30 minutes and still the sync doesn't happen unless I leave the app and come back to it. I am using the same development CloudKit container in all cases
3
5
751
Sep ’25
How to handle required @relationship optionals in SwiftData CloudKit?
Hi all, As you know, when using SwiftData Cloudkit, all relationships are required to be optional. In my app, which is a list app, I have a model class Project that contains an array of Subproject model objects. A Subproject also contains an array of another type of model class and this chain goes on and on. In this type of pattern, it becomes really taxxing to handle the optionals the correct way, i.e. unwrap them as late as possible and display an error to the user if unable to. It seems like most developers don't even bother, they just wrap the array in a computed property that returns an empty array if nil. I'm just wondering what is the recommended way by Apple to handle these optionals. I'm not really familiar with how the CloudKit backend works, but if you have a simple list app that only saves to the users private iCloud, can I just handwave the optionals like so many do? Is it only big data apps that need to worry? Or should we always strive to handle them the correct way? If that's the case, why does it seem like most people skip over them? Be great if an Apple engineer could weigh in.
3
0
163
Oct ’25
CloudKit sync stopped working with error „You can't save and delete the same record"
Hi there We're using CloudKit in our app which, generally, syncs data perfectly between devices. However, recently the sync has stopped working (some changes will never sync and the sync is delayed for several days even with the app open on all devices). CloudKit's logs show the error „You can't save and delete the same record" and „Already have a mirrored relationship registered for this key", etc. We’ve a hunch that this issue is related to a mirrored relationship of one database entity. Our scenario: We've subclassed the database entities. The database model (which we can't share publicly) contains mirrored relationships. We store very long texts in the database (similar to a Word document that contains markup data – in case that’s relevant). Deleting all data and starting with a completely new container and bundle identifier didn’t help (we tried that multiple times). This issue occurs on macOS (15.2(24C101) as well on iOS (18.2). Any hints on how to get the sync working again? Should we simply avoid mirrored relationships? Many thanks
3
0
777
Jan ’25
How to Drop Entity in SwiftData and CloudKit?
I'm using SwiftData with CloudKit and have been trying to migrate from SchemaV1 to SchemaV2, but it seems reducing the Entities crashes my app. // Example of migrating from V1 to V2 // Dropping `Person` because it's no longer needed do { // SchemaV1: Person.self, Author.self // SchemaV2: Author.self let schema = Schema(versionedSchema: SchemaV2.self) return try ModelContainer( for: schema, migrationPlan: AppSchemaMigrationPlan.self, configurations: ModelConfiguration( cloudKitDatabase: .automatic) ) } catch { fatalError("Could not create ModelContainer: \(error)") } Is it possible to drop Entities in the Schema Migration Plan? How can I delete the Person model from my Schema and CloudKit?
3
0
786
Jan ’25