I'm considering using CloudKit in my app (it doesn't use Core Data) and have read as many materials as I can find. I haven't fully grasped it yet and have a basic question on CKRecord.Reference. Does CloudKit guarantee CKRecord.Reference value is always valid? By valid I mean the target CkRecord pointed by the CKRecord.Reference exists in the database. Let's consider an example. Suppose there are two tables: Account and Transaction: Account Table: AccountNumber Currency Rate ------------- -------- ---- a1 USD 0.03 Transaction Table: TransactionNumber AccountNumber Amount ----------------- ------------- ------ t1 a1 20 Now suppose user does the following: User first deletes account a1 and its associated transactions t1 on device A. The device saves the change to cloud. Then user adds a new transaction t2 to account a1 on device B, before the device receives the change made in step 1 from cloud. Since a1 hasn't been deleted on device B, the operation should succeed locally. The device tries to save the change to cloud too. My questions: Q1) Will device B be able to save the change in step 2 to cloud? I hope it would fail, because otherwise it would lead to inconsistent data. But I find the following in CKModifyRecordsOperation doc (emphasis mine), which implies CloudKit allows invalid reference: During a save operation, CloudKit requires that the target record of the parent reference, if set, exists in the database or is part of the same operation; all other reference fields are exempt from this requirement. (BTW, I think the fact that, when using CloudKit, Core Data requires all relations must be optional also indicates that CloudKit can't guarantee relation is always valid, though I think that is mainly an issue on client side caused by data transfer size. The above example, however, is different in that it's an issue on cloud side - the data on cloud is inconsistent). I also find the following in the document. However, I don't think it helps in the above example, because IIUC CloudKit can only detect conflict when the changes on the same record but the changes in step 1 and step 2 are on different records. Because records can change between the time you fetch them and the time you save them, the save policy determines whether new changes overwrite existing changes. By default, the operation reports an error when there’s a newer version on the server. If the above understanding is correct, however, I don't understand why the same document has the following requirement, which implies CloudKit doesn't allow invalid reference: When creating two new records that have a reference between them, use the same operation to save both records at the same time. Q2) Suppose CloudKit allows invalid reference on cloud side (that is, device B successfully saves the change in step 2 to cloud) , I wonder what's the best practice to deal with it? I think the issue is different from the optional relation requirement in Core Data when using CloudKit, because in that case the data is consistent on cloud side and eventually the client will receive complete data. In the above example, however, the data on cloud is inconsistent so the client has to remedy it somehow (although client has little information helping it). One approach I think of is to avoid the issue in the first place. My idea is to maintain a counter in the database and requires client to increase the counter (it's not Lamport clock. BTW, is it possible to use Lamport clock in this case?) when making any change. This should help CloudKit to detect conflict (though I can't think out a good strategy on how client should deal with it. A simple one is perhaps to prompt user to select one copy). However, this approach effectively uses cloud as a centralized server, which I suspect isn't the typical way how people use CloudKit, and it requires clients to maintain local counter value in various situations. I wonder what's the typical approach? Am I missing something? Thanks for any help.

public static func fetch(in context: NSManagedObjectContext, configurationBlock: (NSFetchRequest) -> () = { _ in }) -> [Self] { let request = NSFetchRequest(entityName: Self.entityName) configurationBlock(request) return try! context.fetch(request) } context.fetch(request), 'fetch' function has error. Thread 24: EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)

Swift recently added support for Int128. However, they do need NOT seem to be supported in SwiftData. Now totally possible I'm doing something wrong too. I have the project set to macOS 15 to use a UInt128 in @Model class as attribute. I tried using a clean Xcode project with Swift Data choosen in the macOS app wizard. Everything compiles, but it fails at runtime in both my app and "Xcode default" SwiftData: SwiftData/SchemaProperty.swift:380: Fatal error: Unexpected property within Persisted Struct/Enum: Builtin.Int128 with the only modification to from stock is: @Model final class Item { var timestamp: Date var ipv6: UInt128 init(timestamp: Date) { self.timestamp = timestamp self.ipv6 = 0 } } I have tried both Int128 and UInt128. Both fails exactly the same. In fact, so exactly, when using UInt128 it still show a "Int128" in error message, despite class member being UInt128 . My underlying need is to store an IPv6 addresses with an app, so the newer UInt128 would work to persist it. Since Network Framework IPv6Address is also not compatible, it seems, with SwiftData. So not a lot of good options, other an a String. But for an IPv6 address that suffers from that same address can take a few String forms (i.e. "0000:0000:0000:0000:0000:0000:0000:0000" =="0:0:0:0:0:0:0:0" == "::") which is more annoying than having a few expand Int128 as String separator ":". Ideas welcomed. But potentially a bug in SwiftData since Int128 is both a Builtin and conforms to Codable, so from my reading it should work.

I just released an App update the didn't touch ANYTHING to do with Core Data (nothing changed in our Coredata code for at least 8 months). The update uses SDK for iOS 18 and Xcode 16.2 and the app now requires iOS 18 and was a minor bug patch and UI improvements for recent iOS changes. Since the update we are getting a steady trickle of users on iOS 18, some who allow the App to store data in iCloud (Cloudkit) and others who do not, all reporting that after the update to our recent release ALL their data is gone?! I had not seen this on ANY device until today when I asked a friend who uses the App if they had the issue and it turned out they did, so I hooked their device up to Xcode and ALL the data in the CoreData database was gone?! They are NOT using iCloud. There were no errors or exceptions on Xcode console but a below code returned NO records at all?! Chart is custom entity and is defined as: @interface Chart : NSManagedObject {} let moc = pc.viewContext let chartsFetch = NSFetchRequest<NSFetchRequestResult>(entityName:"Charts") // Fetch all Charts do { let fetchedCharts = try moc.fetch(chartsFetch) as! [Chart] for chart in fetchedCharts { .... } } A break point inside the do on fetchedCharts show there are NO objects returned. This is a serious issue and seems like an iOS 18 thing. I saw some people talking in here about NSFetchRequest issues with iOS 18. I need some guidance here from someone Apple engineer here who knows what the status of these NSFetchrequest bugs are and what possible workarounds are. Becasue this problem will grow for me as more users update to iOS 18.

Hi, I have designed an app which needs to reschedule notifications according to the user's calendar at midnight. The function has been implemented successfully via backgroundtask. But since the app has enabled iCloud sync, some users will edit their calendar on their iPad and expect that the notifications will be sent promptly to them on iPhone without launching the app on their iPhone. But the problem is that if they haven't launched the app on their iPhone, iCloud sync won't happen. The notifications on their iPhone haven't been updated and will be sent wrongly. How can I design some codes to let iCloud sync across the devices without launching the app at midnight and then reschedule notifications?

Hi, I did cloudkit synchronization using swiftdata. However, synchronization does not occur automatically, and synchronization occurs intermittently only when the device is closed and opened. For confirmation, after changing the data in Device 1 (saving), when the data is fetched from Device 2, there is no change. I've heard that there's still an issue with swiftdata sync and Apple is currently troubleshooting it, is the phenomenon I'm experiencing in the current version normal?

After a recent iOS update, my app is not synching between devices. I'm not seeing or getting any errors. CLoudKit Logs show activity, but it's not happening realtime. Even if I close and reopen the app, it won't sync between devices. It almost looks like it only has local storage now and CloudKit is not working on it anymore. STEPS TO REPRODUCE Use app on two devices with the same Apple ID. Create a user and one device and it won't show up on the other device. Vice Versa.

DESCRIPTION I have an App use iCloud to save data. The App had a CoreData ManagedObject 'Product', 'Product' Object had an attribute name 'count' and it is a Double Type. I need to synchronises 'count' property across multiple devices. for example: I have a devices A、B. A device set 'Product.count' = 100. B device set 'Product.count' = 50. I hope the 'Product.count' == 150 that results. how to synchronises the 'Product.count' == 150 for multiple devices. If I have more devices in future, How to get the latest 'Product.count' that it is correct result.

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

I'm trying to write a SwiftUI iOS/macOS app that allows users to collaborate, but I keep running into limitations. The latest is that I can't figure out what the UICloudSharingContainer equivalent is on macOS. It doesn't seem like there’s a SwiftUI version of this, so I have to write a lot of platform-specific code to handle it, but it's not clear what the AppKit equivalent is.

Use CloudKit's ckqueryoperation's recordmatchedblock in Swift 6.0, which always crashes, but works fine in Swift 5: func fetchAllRecords() async throws { let predicate = NSPredicate(format: "Topics = %@", "Integrations") let query = CKQuery(recordType: "PureMList", predicate: predicate) let operation = CKQueryOperation(query: query) operation.recordMatchedBlock = { recordID, result in switch result { case .success(let record): DispatchQueue.main.async { // Ensure UI updates happen here print("Fetched record: \(record)") // Update your UI elements here } case .failure(let error): // Handle the error print("Error fetching record with ID \(recordID): \(error)") } } // Ensure you're using the correct database publicDatabase.add(operation) }

I have an app that starts a Live Activity on a certain user action. This Live Activity contains a button that the user can tap, which updates a SwiftData model instance. However, when you return to the main app after tapping the button on the Live Activity, the views do not update to reflect the changes, even though the changes were written to the database. The underlying issue here is that the ModelContainer/ModelContext used by the AppIntent (performed from the LiveActivity when the button is tapped), are different from the instances in the main app. Meaning that while the changes are written to the underlying storage, the in-memory instances of ModelContext/ModelContainer in the main app don't get the changes from the extension, so SwiftUI doesn't update either. What is the recommended way to handle this scenario? Or is there one? :) Shared access to a SwiftData container is clearly supported through App Groups, so is there not a mechanism to ensure changes made by an extension are updated in real-time for the main app? Otherwise, it seems I would have to go through and manually rerun queries that views depend on to make sure they are showing the most recent data. This is cumbersome and error-prone. Perhaps I'm missing something? Any suggestions would be greatly appreciated.

I'm running into an undocumented error coming back from CloudKit operations. Specifically, I'm attempting to save new records via CKModifyRecordsOperation. I'm receiving this error for each of the records in the perRecordSaveBlock callback: &lt;CKError 0x3018ac3c0: "Internal Error" (1/3001); "MMCSEngineCreate failed"&gt; Is anyone else facing this error? It has been happening for several days and I'm finally getting around to reproduction with the Console app and logs. I have 16 records on my device locally that each one gets this error back. FB16547732 - CloudKit: CKModifyRecordsOperation saving new records results in Error &lt;CKError 0x3018ac1e0: "Internal Error" (1/3001); "MMCSEngineCreate failed"&gt;

I am running into some issues when trying to destroy CoreData persistentStores. When a user logs out of my app, I want to completely reset CoreData and delete any existing data. My code to reset CoreData looks like this: let coordinator = self.persistentContainer.persistentStoreCoordinator self.persistentContainer.viewContext.reset() coordinator.persistentStores.forEach { store in guard let url = store.url else { return } do { try coordinator.destroyPersistentStore(at: url, type: .sqlite) _ = try coordinator.addPersistentStore(ofType: NSSQLiteStoreType, configurationName: nil, at: url) } catch { print(error) } } However, my app is crashing with Object 0xb2b5cc80445813de <x-coredata://BDB999D4-49A4-4CB3-AC3A-666AD60BEFC6/AccountEntity/p5> persistent store is not reachable from this NSManagedObjectContext's coordinator It seems this is related to the SwiftUI @FetchRequest wrappers. If I do not open the views where I am using @FetchRequest, the logout goes smoothly. Otherwise, I get the crash above. Has anyone run into anything similar? Is there something else I need to do to get the underlying FRC to release its references to those entities? I was under the impression that calling reset() on the managed object context would be enough to remove those items from memory and get the destroying of the persistent store to go smoothly. Alternately, is there another/better way I should be destroying the DB? Any advice or related observations would be greatly appreciated. Thank you!

I'm trying to get the CoreDataCloudKitShare example to work, but having trouble. The first error I see when running the InitializeCloudKitSchema target (on macOS) is the following: error: CoreData+CloudKit: -[NSCloudKitMirroringDelegate _performSetupRequest:]_block_invoke(1242): <NSCloudKitMirroringDelegate: 0x60000229c0f0>: Failed to set up CloudKit integration for store: <NSSQLCore: 0x15b807830> (URL: file:///Users/rmann/Library/Application%20Support/InitializeCloudKitSchema/CoreDataStores/Private/private.sqlite) <CKError 0x600001311290: "Partial Failure" (2/1011); "Failed to modify some record zones"; uuid = 3E1B1380-AE1C-4B14-97A8-7F60B4A8F3EF; container ID = "iCloud.com.example.CoreDataCloudKitShareH6F2W964VK"; partial errors: { com.apple.coredata.cloudkit.zone:__defaultOwner__ = <CKError 0x60000132f810: "Permission Failure" (10/2007); server message = "Invalid bundle ID for container"; op = F3987848B25CEED7; uuid = 3E1B1380-AE1C-4B14-97A8-7F60B4A8F3EF> }> I see a database in the Dashboard with that container ID, but don't know what it means by "Invalid bundle ID for container". I've seen several other posts about this across the web, and the only answer is ever "seems to be an Apple issue, wait a bit."

My app is able to receive data updates when it is in foreground. however, when i move it in background then sync engine stops syncing until I again move app to foreground.

In Apple Numbers and similar apps, a user can save a document to iCloud Drive, and collaborate with other users. From what I can gather, it seems to use two mechanisms: the document as a whole is synced via iCloud Drive, but when a collaboration is started, it seems to use CloudKit records to do live updates. I am working on a similar app, that saves documents to iCloud Drive (on Mac, iPad, and iPhone). Currently it only syncs via iCloud Drive, re-reading the entire (often large) document when a remote change occurs. This can lead to a delay of several seconds (up to a minute) for the document to be saved, synced to the server, synced from the server, and re-read. I'm working on adding a "live sync", i.e. the ability to see changes in as near to real-time as feasible, like in Apple's apps. The document as a whole will remain syncing via iCloud Drive. My thought is to add a CloudKit CKRecord-based sync when two or more users are collaborating on a document, recording only the diffs for quick updates. The app would no longer re-read the entire document when iCloud Drive updates it while in use, and would instead read the CloudKit records and apply those changes. This should be much faster. Is my understanding of how Apple does it correct? Does my proposed approach seem sensible? Has anyone else implemented something like this, with iCloud Drive-based documents and a CloudKit live sync? In terms of technologies, I see that Apple now has a Shared with You framework, with the ability to use a NSItemProvider to start the collaboration. Which raises the question, should I use the iCloud Drive document for the collaboration (as I do now), or the CloudKit CKShare diff? I think I'd have to use the document as a whole, both so it works with the Send Copy option, and so a user that doesn't have the document gets it when using Collaborate. Once the collaboration is underway, I'd want to start the CloudKit channel. So I guess I'd save the CKShare to the server, get its URL, and save that in the document, so another user can read that URL as part of their initial load of the document from iCloud Drive? Once two (or more) users have the document via iCloud Drive, and the CKShare via the embedded URL, I should be able to do further live-sync updates via CloudKit. If a user closes the document and re-opens it, they'd get the updates via iCloud Drive, so no need to apply any updates from before the document was opened. Does all this sound reasonable, or am I overlooking some gotcha? I'd appreciate any advice from people who have experience with this kind of syncing.

I have a Live Activity with a button that updates a SwiftData model. This used to work in iOS 17, but not on iOS 18. The reason is that in iOS 17, when you run an AppIntent from a Live Activity, the perform() method would run in the main app's process, meaning it had access to the app's ModelContainer/ModelContext. However, in iOS 18, this is no longer the case, and the perform() method of an AppIntent now runs in the extension's process. While I can still construct a new ModelContainer & ModelContext in the AppIntent's perform() method, the main app's container and context will not see these changes until the app is relaunched. How can I make this work in iOS 18 now that an AppIntent executed from an extension runs in a different process from the main app?

Consider this code @UIApplicationDelegateAdaptor(AppDelegate.self) var appDelegate init() { let schema = Schema([ ... ]) let modelConfiguration = ModelConfiguration(schema: schema, isStoredInMemoryOnly: false) do { sharedModelContainer = try ModelContainer(for: schema, configurations: [modelConfiguration]) } catch { fatalError("Could not create ModelContainer: \(error)") } SettingsViewModel.shared = SettingsViewModel(modelContext: sharedModelContainer.mainContext) } I'm basically saving a copy of mainContext in a viewModel. And then later on uses that viewModel to operate on the models while using the mainActor. Is this ok? That same container is also pass into the view using .modelContainer(sharedModelContainer) Can it be used in both ways like that?

The SwiftUI templates provided by Xcode typically create an in-memory store for preview purposes. I started from one of these templates and added the necessary code for working with CloudKit shares, but now the existing preview store creation gets runtime errors I'm struggling to understand. The ultimate error is: FAULT: NSInternalInconsistencyException: Unsupported feature in this configuration; { store = "<NSSQLCore: 0x12e26b170> (URL: file:///dev/null)"; } There are other things in the log like: warning: Multiple NSEntityDescriptions claim the NSManagedObject subclass 'Trip' so +entity is unable to disambiguate. This might be due in part to the normal full stack being instantiated during a unit test, but that was the only way I could step through the code to try to see what was causing the SwiftUI preview to crash. I can't build the full core data stack as normal, because then the unit tests and previews pollute the real store.