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Core Data initialization causes app to deadlock on startup
Users have been reporting that the TestFlight version of my app (compiled with Xcode 26 Beta 6 17A5305f) is sometimes crashing on startup. Upon investigating their ips files, it looks like Core Data is locking up internally during its initialization, resulting in iOS killing my app. I have not recently changed my Core Data initialization logic, and it's unclear how I should proceed. Is this a known issue? Any recommended workaround? I have attached the crash stack below. Thanks! crash_log.txt
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244
Sep ’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
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Sep ’25
Old CloudKit Data Repopulating after a Local Reset
We are trying to solve for the following condition with SwiftData + CloudKit: Lots of data in CloudKit Perform "app-reset" to clear data & App settings and start fresh. Reset data models with try modelContext.delete(model:_) myModel.count() confirms local deletion (0 records); but iCloud Console shows expectedly slow process to delete. Old CloudKit data is returning during the On Boarding process. Questions: • Would making a new iCloud Zone for each reset work around this, as the new zone would be empty? We're having trouble finding details about how to do this with SwiftData. • Would CKSyncEngine have a benefit over the default SwiftData methods? Open to hearing if anyone has experienced a similar challenge and how you worked around it!
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259
Jun ’25
SQLite strftime() support with Core Data FetchRequest
My entity has a startDate (NSTime) attribute where I use the date and time in my detail display of the entity. And in my list, I need to group my entities by day (YYMMDD) based on the start date; and I want to ensure that it can adapt to the region where the user is currently (e.g. if user travels or migrate, the YYMMDD should be adapted based on the current region). Does Core Data SectionedFetchRequest supports strftime() functions from SQLite (https://sqlite.org/lang_datefunc.html) or what is an effective alternative sectioned fetch in my case?
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403
Sep ’25
Widget error upon restore iPhone: The file "Name.sqlite" couldn't be opened
I have an app that uses NSPersistentCloudKitContainer stored in a shared location via App Groups so my widget can fetch data to display. It works. But if you reset your iPhone and restore it from a backup, an error occurs: The file "Name.sqlite" couldn't be opened. I suspect this happens because the widget is created before the app's data is restored. Restarting the iPhone is the only way to fix it though, opening the app and reloading timelines does not. Anything I can do to fix that to not require turning it off and on again?
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330
Jul ’25
CloudKit shares and iOS26 public beta (23A5336a)
I am developing an app that uses CloudKit sharing. I recently upgraded my iPad to use 23A5336a. After that upgrade, I can no longer accept a share that is sent to me. I have rebooted the iPad and logged out of the iCloud account and logged back in. Every time I get a share link and tap it, it says: " The owner stopped sharing or your account (xxx) doesn't have permission to open it" This same code, running on the iOS26 device can share with device running iOS18. Is this a known defect? Anything I can do to help resolve this issue?
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267
Sep ’25
Using SwiftData with a local and CloudKit backed configuration at the same time
I'm trying to set up an application using SwiftData to have a number of models backed by a local datastore that's not synced to CloudKit, and another set of models that is. I was able to achieve this previously with Core Data using multiple NSPersistentStoreDescription instances. The set up code looks something like: do { let fullSchema = Schema([ UnsyncedModel.self, SyncedModel.self, ]) let localSchema = Schema([UnsyncedModel.self]) let localConfig = ModelConfiguration(schema: localSchema, cloudKitDatabase: .none) let remoteSchema = Schema([SyncedModel.self]) let remoteConfig = ModelConfiguration(schema: remoteSchema, cloudKitDatabase: .automatic) container = try ModelContainer(for: fullSchema, configurations: localConfig, remoteConfig) } catch { fatalError("Failed to configure SwiftData container.") } However, it doesn't seem to work as expected. If I remove the synced/remote schema and configuration then everything works fine, but the moment I add in the remote schema and configuration I get various different application crashes. Some examples below: A Core Data error occurred." UserInfo={Reason=Entity named:... not found for relationship named:..., Fatal error: Failed to identify a store that can hold instances of SwiftData._KKMDBackingData<...> Has anyone ever been able to get a similar setup to work using SwiftData?
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Oct ’25
Unable to sync SwiftData model fully using CloudKit
Hey everyone I just ran into an issue where I couldn't sync the model below fully by using CloudKit, enum LinkMapV3_1: VersionedSchema { static let versionIdentifier: Schema.Version = .init(3, 1, 0) static var models: [any PersistentModel.Type] { [AnnotationData.self, GroupData.self, Item.self, Deployment.self, History.self] } // MARK: - Data @Model class AnnotationData { var name: String = "" var longitude: Double = 0.0 var latitude: Double = 0.0 var order: Int = -1 var level: Int = 1 var detail: String = "" @Relationship(deleteRule: .nullify, inverse: \GroupData.annotation) var groups: [GroupData]? @Relationship(deleteRule: .nullify, inverse: \AnnotationData.to) var from: AnnotationData? var to: AnnotationData? var history: History? } // MARK: - History @Model class History { var id: UUID = UUID() var timestamp: Date = Date() @Relationship(deleteRule: .nullify, inverse: \AnnotationData.history) var annotations: [AnnotationData]? @Relationship(deleteRule: .nullify, inverse: \GroupData.history) var groups: [GroupData]? @Relationship(deleteRule: .nullify, inverse: \Item.history) var items: [Item]? @Relationship(deleteRule: .nullify, inverse: \Deployment.history) var deployment: Deployment? var formattedDate: String { let formatter = DateFormatter() formatter.dateStyle = .medium formatter.timeStyle = .short return formatter.string(from: timestamp) } var timeAgo: String { let formatter = RelativeDateTimeFormatter() formatter.unitsStyle = .abbreviated return formatter.localizedString(for: timestamp, relativeTo: Date()) } } } So when trying to sync with the code in documentation let modelContainer: ModelContainer init() { let config = ModelConfiguration() typealias vs = LinkMapV3_1 do { #if DEBUG // Use an autorelease pool to make sure Swift deallocates the persistent // container before setting up the SwiftData stack. try autoreleasepool { let desc = NSPersistentStoreDescription(url: config.url) let opts = NSPersistentCloudKitContainerOptions(containerIdentifier: "iCloud.name.Endsunset.LinkMap.SwiftData.v1") desc.cloudKitContainerOptions = opts // Load the store synchronously so it completes before initializing the // CloudKit schema. desc.shouldAddStoreAsynchronously = false if let mom = NSManagedObjectModel.makeManagedObjectModel(for: [vs.AnnotationData.self, vs.GroupData.self, vs.Item.self, vs.Deployment.self, vs.History.self]) { let container = NSPersistentCloudKitContainer(name: "LinkMap", managedObjectModel: mom) container.persistentStoreDescriptions = [desc] container.loadPersistentStores {_, err in if let err { fatalError(err.localizedDescription) } } // Initialize the CloudKit schema after the store finishes loading. try container.initializeCloudKitSchema() // Remove and unload the store from the persistent container. if let store = container.persistentStoreCoordinator.persistentStores.first { try container.persistentStoreCoordinator.remove(store) } } } #endif modelContainer = try ModelContainer(for: vs.AnnotationData.self, vs.GroupData.self, vs.Item.self, vs.Deployment.self, vs.History.self, configurations: config) } catch { fatalError(error.localizedDescription) } } The output is Console Output Where you can see Output Extract Optional arrays with @Relationship are missing, and the entry of record types on cloudkit database container are also missing it. When I attempt to insert an annotation, I got SwiftData/PersistentModel.swift:559: Fatal error: This KeyPath does not appear to relate AnnotationData to anything - \AnnotationData.groups It gets more suspicious when restart the app and try again, the above error end with "AnnotationData.history", and if I tried again the above error end with "AnnotationData.from"... and so on. No matter how my app stop working.
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Jan ’26
How to switch between Core Data Persistent Stores?
What is the best way to switch between Core Data Persistent Stores? My use case is that I have a multi-user app that stores thousands of data items unique to each user. To me, having Persistent Stores for each user seems like the best design to keep their data separate and private. (If anyone believes that storing the data for all users in one Persistent Store is a better design, I'd appreciate hearing from them.) Customers might switch users 5 to 10 times a day. Switching users must be fast, say a second or two at most.
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Jun ’25
joblinkapp's registerview problem
我正在使用 Core Data 开发一个 SwiftUI 项目。我的数据模型中有一个名为 AppleUser 的实体,具有以下属性:id (UUID)、name (String)、email (String)、password (String) 和 createdAt (Date)。所有属性都是非可选的。 我使用 Xcode 的自动生成创建了相应的 Core Data 类文件(AppleUser+CoreDataClass.swift 和 AppleUser+CoreDataProperties.swift)。我还有一个 PersistenceController,它使用模型名称 JobLinkModel 初始化 NSPersistentContainer。 当我尝试使用以下方法保存新的 AppleUser 对象时: 让用户 = AppleUser(上下文:viewContext) user.id = UUID() user.name = “用户 1” user.email = “...” user.password = “密码 1” user.createdAt = Date()【电子邮件格式正确,但已替换为“...”出于隐私原因】 尝试?viewContext.save() 我在控制台中收到以下错误:核心数据保存失败:Foundation._GenericObjCError.nilError, [:] 用户快照: [“id”: ..., “name”: “User1”, “email”: “...”, “password”: “...”, “createdAt”: ...] 所有字段都有有效值,核心数据模型似乎正确。我还尝试过: • 检查 NSPersistentContainer(name:) 中的模型名称是否与 .xcdatamodeld 文件 (JobLinkModel) 匹配 • 确保正确设置 AppleUser 实体类、模块和 Codegen(类定义、当前产品模块) • 删除重复或旧的 AppleUser 类文件 • 清理 Xcode 构建文件夹并从模拟器中删除应用程序 • 对上下文使用 @Environment(.managedObjectContext) 尽管如此,在保存新的 AppleUser 对象时,我仍然会收到 _GenericObjCError.nilError。 我想了解: 为什么即使所有字段都不是零且正确分配,核心数据也无法保存? 这可能是由于一些残留的旧类文件引起的,还是我缺少设置中的其他内容? 我应该采取哪些步骤来确保 Core Data 正确识别 AppleUser 实体并允许保存? 任何帮助或指导将不胜感激。
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Sep ’25
Using relationships in SortDescriptor crashing on release
If use a SortDescriptor for a model and sort by some attribute from a relationship, in DEBUG mode it all works fine and sorts. However, in release mode, it is an instant crash. SortDescriptor(.name, order: .reverse) ---- works SortDescriptor(.assignedUser?.name, order: .reverse) ---- works in debug but crash in release. What is the issue here, is it that SwiftData just incompetent to do this?
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Aug ’25
SwiftData: filtering against an array of PersistentIdentifiers
I would like to have a SwiftData predicate that filters against an array of PersistentIdentifiers. A trivial use case could filtering Posts by one or more Categories. This sounds like something that must be trivial to do. When doing the following, however: let categoryIds: [PersistentIdentifier] = categoryFilter.map { $0.id } let pred = #Predicate<Post> { if let catId = $0.category?.persistentModelID { return categoryIds.contains(catId) } else { return false } } The code compiles, but produces the following runtime exception (XCode 26 beta, iOS 26 simulator): 'NSInvalidArgumentException', reason: 'unimplemented SQL generation for predicate : (TERNARY(item != nil, item, nil) IN {}) (bad LHS)' Strangely, the same code works if the array to filter against is an array of a primitive type, e.g. String or Int. What is going wrong here and what could be a possible workaround?
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Jun ’25
Mutating an array of model objects that is a child of a model object
Hi all, In my SwiftUI / SwiftData / Cloudkit app which is a series of lists, I have a model object called Project which contains an array of model objects called subprojects: final class Project1 { var name: String = "" @Relationship(deleteRule: .cascade, inverse: \Subproject.project) var subprojects : [Subproject]? init(name: String) { self.name = name self.subprojects = [] } } The user will select a project from a list, which will generate a list of subprojects in another list, and if they select a subproject, it will generate a list categories and if the user selects a category it will generate another list of child objects owned by category and on and on. This is the pattern in my app, I'm constantly passing arrays of model objects that are the children of other model objects throughout the program, and I need the user to be able to add and remove things from them. My initial approach was to pass these arrays as bindings so that I'd be able to mutate them. This worked for the most part but there were two problems: it was a lot of custom binding code and when I had to unwrap these bindings using init?(_ base: Binding<Value?>), my program would crash if one of these arrays became nil (it's some weird quirk of that init that I don't understand at al). As I'm still learning the framework, I had not realized that the @model macro had automatically made my model objects observable, so I decided to remove the bindings and simply pass the arrays by reference, and while it seems these references will carry the most up to date version of the array, you cannot mutate them unless you have access to the parent and mutate it like such: project.subcategories?.removeAll { $0 == subcategory } project.subcategories?.append(subcategory) This is weirding me out because you can't unwrap subcategories before you try to mutate the array, it has to be done like above. In my code, I like to unwrap all optionals at the moment that I need the values stored in them and if not, I like to post an error to the user. Isn't that the point of optionals? So I don't understand why it's like this and ultimately am wondering if I'm using the correct design pattern for what I'm trying to accomplish or if I'm missing something? Any input would be much appreciated! Also, I do have a small MRE project if the explanation above wasn't clear enough, but I was unable to paste in here (too long), attach the zip or paste a link to Google Drive. Open to sharing it if anyone can tell me the best way to do so. Thanks!
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Sep ’25
Core Data Multiple NSEntityDescriptions claim the NSManagedObject subclass
Hello everyone, I'm trying to adopt the new Staged Migrations for Core Data and I keep running into an error that I haven't been able to resolve. The error messages are as follows: warning: Multiple NSEntityDescriptions claim the NSManagedObject subclass 'Movie' so +entity is unable to disambiguate. warning: 'Movie' (0x60000350d6b0) from NSManagedObjectModel (0x60000213a8a0) claims 'Movie'. error: +[Movie entity] Failed to find a unique match for an NSEntityDescription to a managed object subclass This happens for all of my entities when they are added/fetched. Movie is an abstract entity subclass, and it has the error error: +[Movie entity] Failed to find which is unique to the subclass entities, but this occurs for all entities. The NSPersistentContainer is loaded only once, and I set the following option after it's loaded: storeDescription.setOption( [stages], forKey: NSPersistentStoreStagedMigrationManagerOptionKey ) The warnings and errors only appear after I fetch or save to context. It happens regardless of whether the database was migrated or not. In my test project, using the generic NSManagedObject with NSEntityDescription.insertNewObject(forEntityName: "MyEntity", into: context) does not cause the issue. However, using the generic NSManagedObject is not a viable option for my app. Setting the module to "Current Project Module" doesn't change anything, except that it now prints "claims 'MyModule.Show'" in the warnings. I have verified that there are no other entities with the same name or renameIdentifier. Has anyone else encountered this issue, or can offer any suggestions on how to resolve it? Thanks in advance for any help!
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4d
NSPersistentCloudKitContainer causes crash on watchOS when device is offline
Hi. I'm hoping someone might be able to help us with an issue that's been affecting our standalone watchOS app for some time now. We've encountered consistent crashes on Apple Watch devices when the app enters the background while the device is offline (i.e., no Bluetooth and no Wi-Fi connection). Through extensive testing, we've isolated the problem to the use of NSPersistentCloudKitContainer. When we switch to NSPersistentContainer, the crashes no longer occur. Interestingly, this issue only affects our watchOS app. The same CloudKit-based persistence setup works reliably on our iOS and macOS apps, even when offline. This leads us to believe the issue may be specific to how NSPersistentCloudKitContainer behaves on watchOS when the device is disconnected from the network. We're targeting watchOS 10 and above. We're unsure if this is a misconfiguration on our end or a potential system-level issue, and we would greatly appreciate any insight or guidance.
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Jun ’25
Core Data, Swift 6, Concurrency and more
I have the following struct doing some simple tasks, running a network request and then saving items to Core Data. Per Xcode 26's new default settings (onisolated(nonsending) & defaultIsolation set to MainActor), the struct and its functions run on the main actor, which works fine and I can even safely omit the context.perform call because of it, which is great. struct DataHandler { func importGames(withIDs ids: [Int]) async throws { ... let context = PersistenceController.shared.container.viewContext for game in games { let newGame = GYGame(context: context) newGame.id = UUID() } try context.save() } } Now, I want to run this in a background thread to increase performance and responsiveness. So I followed this session (https://developer.apple.com/videos/play/wwdc2025/270) and believe the solution is to mark the struct as nonisolated and the function itself as @concurrent. The function now works on a background thread, but I receive a crash: _dispatch_assert_queue_fail. This happens whether I wrap the Core Data calls with context.perform or not. Alongside that I get a few new warnings which I have no idea how to work around. So, what am I doing wrong here? What's the correct way to solve this simple use case with Swift 6's new concurrency stuff and the default main actor isolation in Xcode 26? Curiously enough, when setting onisolated(nonsending) to false & defaultIsolation to non isolating, mimicking the previous behavior, the function works without crashing. nonisolated struct DataHandler { @concurrent func importGames(withIDs ids: [Int]) async throws { ... let context = await PersistenceController.shared.container.newBackgroundContext() for game in games { let newGame = GYGame(context: context) newGame.id = UUID() // Main actor-isolated property 'id' can not be mutated from a nonisolated context; this is an error in the Swift 6 language mode } try context.save() } }
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Jun ’25
defaultIsolation option and Core Data
When creating a new project in Xcode 26, the default for defaultIsolation is MainActor. Core Data creates classes for each entity using code gen, but now those classes are also internally marked as MainActor, which causes issues when accessing managed object from a background thread like this. Is there a way to fix this warning or should Xcode actually mark these auto generated classes as nonisolated to make this better? Filed as FB13840800. nonisolated struct BackgroundDataHandler { @concurrent func saveItem() async throws { let context = await PersistenceController.shared.container.newBackgroundContext() try await context.perform { let newGame = Item(context: context) newGame.timestamp = Date.now // Main actor-isolated property 'timestamp' can not be mutated from a nonisolated context; this is an error in the Swift 6 language mode try context.save() } } } Turning code gen off inside the model and creating it manually, with the nonisolated keyword, gets rid of the warning and still works fine. So I guess the auto generated class could adopt this as well? public import Foundation public import CoreData public typealias ItemCoreDataClassSet = NSSet @objc(Item) nonisolated public class Item: NSManagedObject { }
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Jun ’25
Invalid bundle ID for container
Hi. I am having this error when trying to write to CloudKit public database. <CKError 0x600000dbc4e0: "Permission Failure" (10/2007); server message = "Invalid bundle ID for container"; On app launch, I check for account status and ensure that the correct bundle identifier and container is being used. When the account status is checked, I do get the correct bundle id and container id printed in the console but trying to read or write to the container would throw that "Invalid bundle ID for container" error. private init() { container = CKContainer.default() publicDB = container.publicCloudDatabase // Check iCloud account status checkAccountStatus() } func checkAccountStatus() { print("🔍 CloudKit Debug:") print("🔍 Bundle identifier from app: (Bundle.main.bundleIdentifier ?? "unknown")") print("🔍 Container identifier: (container.containerIdentifier ?? "unknown")") container.accountStatus { [weak self] status, error in DispatchQueue.main.async { switch status { case .available: self?.isSignedIn = true self?.fetchUserID() case .noAccount, .restricted, .couldNotDetermine: self?.isSignedIn = false self?.errorMessage = "Please sign in to iCloud in Settings to use this app." default: self?.isSignedIn = false self?.errorMessage = "Unknown iCloud account status." } print("User is signed into iCloud: \(self?.isSignedIn ?? false)") print("Account status: \(status.rawValue)") } } } I have tried: Creating a new container Unselecting and selecting the container in signing & capabilities Unselecting and selecting the container in App ID Configuration I used to have swift data models in my code and read that swift data is not compatible with CloudKit public data so I removed all the models and any swift data codes and only uses CloudKit public database. let savedRecord = try await publicDB.save(record) Nothing seems to work. If anyone could help please? Rgds, Hans
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Jun ’25
Core Data initialization causes app to deadlock on startup
Users have been reporting that the TestFlight version of my app (compiled with Xcode 26 Beta 6 17A5305f) is sometimes crashing on startup. Upon investigating their ips files, it looks like Core Data is locking up internally during its initialization, resulting in iOS killing my app. I have not recently changed my Core Data initialization logic, and it's unclear how I should proceed. Is this a known issue? Any recommended workaround? I have attached the crash stack below. Thanks! crash_log.txt
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2
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244
Activity
Sep ’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
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3
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478
Activity
Sep ’25
Old CloudKit Data Repopulating after a Local Reset
We are trying to solve for the following condition with SwiftData + CloudKit: Lots of data in CloudKit Perform "app-reset" to clear data & App settings and start fresh. Reset data models with try modelContext.delete(model:_) myModel.count() confirms local deletion (0 records); but iCloud Console shows expectedly slow process to delete. Old CloudKit data is returning during the On Boarding process. Questions: • Would making a new iCloud Zone for each reset work around this, as the new zone would be empty? We're having trouble finding details about how to do this with SwiftData. • Would CKSyncEngine have a benefit over the default SwiftData methods? Open to hearing if anyone has experienced a similar challenge and how you worked around it!
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2
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259
Activity
Jun ’25
SQLite strftime() support with Core Data FetchRequest
My entity has a startDate (NSTime) attribute where I use the date and time in my detail display of the entity. And in my list, I need to group my entities by day (YYMMDD) based on the start date; and I want to ensure that it can adapt to the region where the user is currently (e.g. if user travels or migrate, the YYMMDD should be adapted based on the current region). Does Core Data SectionedFetchRequest supports strftime() functions from SQLite (https://sqlite.org/lang_datefunc.html) or what is an effective alternative sectioned fetch in my case?
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1
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403
Activity
Sep ’25
Widget error upon restore iPhone: The file "Name.sqlite" couldn't be opened
I have an app that uses NSPersistentCloudKitContainer stored in a shared location via App Groups so my widget can fetch data to display. It works. But if you reset your iPhone and restore it from a backup, an error occurs: The file "Name.sqlite" couldn't be opened. I suspect this happens because the widget is created before the app's data is restored. Restarting the iPhone is the only way to fix it though, opening the app and reloading timelines does not. Anything I can do to fix that to not require turning it off and on again?
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12
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330
Activity
Jul ’25
CloudKit shares and iOS26 public beta (23A5336a)
I am developing an app that uses CloudKit sharing. I recently upgraded my iPad to use 23A5336a. After that upgrade, I can no longer accept a share that is sent to me. I have rebooted the iPad and logged out of the iCloud account and logged back in. Every time I get a share link and tap it, it says: " The owner stopped sharing or your account (xxx) doesn't have permission to open it" This same code, running on the iOS26 device can share with device running iOS18. Is this a known defect? Anything I can do to help resolve this issue?
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1
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267
Activity
Sep ’25
Using SwiftData with a local and CloudKit backed configuration at the same time
I'm trying to set up an application using SwiftData to have a number of models backed by a local datastore that's not synced to CloudKit, and another set of models that is. I was able to achieve this previously with Core Data using multiple NSPersistentStoreDescription instances. The set up code looks something like: do { let fullSchema = Schema([ UnsyncedModel.self, SyncedModel.self, ]) let localSchema = Schema([UnsyncedModel.self]) let localConfig = ModelConfiguration(schema: localSchema, cloudKitDatabase: .none) let remoteSchema = Schema([SyncedModel.self]) let remoteConfig = ModelConfiguration(schema: remoteSchema, cloudKitDatabase: .automatic) container = try ModelContainer(for: fullSchema, configurations: localConfig, remoteConfig) } catch { fatalError("Failed to configure SwiftData container.") } However, it doesn't seem to work as expected. If I remove the synced/remote schema and configuration then everything works fine, but the moment I add in the remote schema and configuration I get various different application crashes. Some examples below: A Core Data error occurred." UserInfo={Reason=Entity named:... not found for relationship named:..., Fatal error: Failed to identify a store that can hold instances of SwiftData._KKMDBackingData<...> Has anyone ever been able to get a similar setup to work using SwiftData?
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428
Activity
Oct ’25
I have a problem with an entity in the core data
When I try to use an entity created in a CoreData, it gives me: 'PlayerData' is ambiguous for type lookup in this context
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103
Activity
Jun ’25
Unable to sync SwiftData model fully using CloudKit
Hey everyone I just ran into an issue where I couldn't sync the model below fully by using CloudKit, enum LinkMapV3_1: VersionedSchema { static let versionIdentifier: Schema.Version = .init(3, 1, 0) static var models: [any PersistentModel.Type] { [AnnotationData.self, GroupData.self, Item.self, Deployment.self, History.self] } // MARK: - Data @Model class AnnotationData { var name: String = "" var longitude: Double = 0.0 var latitude: Double = 0.0 var order: Int = -1 var level: Int = 1 var detail: String = "" @Relationship(deleteRule: .nullify, inverse: \GroupData.annotation) var groups: [GroupData]? @Relationship(deleteRule: .nullify, inverse: \AnnotationData.to) var from: AnnotationData? var to: AnnotationData? var history: History? } // MARK: - History @Model class History { var id: UUID = UUID() var timestamp: Date = Date() @Relationship(deleteRule: .nullify, inverse: \AnnotationData.history) var annotations: [AnnotationData]? @Relationship(deleteRule: .nullify, inverse: \GroupData.history) var groups: [GroupData]? @Relationship(deleteRule: .nullify, inverse: \Item.history) var items: [Item]? @Relationship(deleteRule: .nullify, inverse: \Deployment.history) var deployment: Deployment? var formattedDate: String { let formatter = DateFormatter() formatter.dateStyle = .medium formatter.timeStyle = .short return formatter.string(from: timestamp) } var timeAgo: String { let formatter = RelativeDateTimeFormatter() formatter.unitsStyle = .abbreviated return formatter.localizedString(for: timestamp, relativeTo: Date()) } } } So when trying to sync with the code in documentation let modelContainer: ModelContainer init() { let config = ModelConfiguration() typealias vs = LinkMapV3_1 do { #if DEBUG // Use an autorelease pool to make sure Swift deallocates the persistent // container before setting up the SwiftData stack. try autoreleasepool { let desc = NSPersistentStoreDescription(url: config.url) let opts = NSPersistentCloudKitContainerOptions(containerIdentifier: "iCloud.name.Endsunset.LinkMap.SwiftData.v1") desc.cloudKitContainerOptions = opts // Load the store synchronously so it completes before initializing the // CloudKit schema. desc.shouldAddStoreAsynchronously = false if let mom = NSManagedObjectModel.makeManagedObjectModel(for: [vs.AnnotationData.self, vs.GroupData.self, vs.Item.self, vs.Deployment.self, vs.History.self]) { let container = NSPersistentCloudKitContainer(name: "LinkMap", managedObjectModel: mom) container.persistentStoreDescriptions = [desc] container.loadPersistentStores {_, err in if let err { fatalError(err.localizedDescription) } } // Initialize the CloudKit schema after the store finishes loading. try container.initializeCloudKitSchema() // Remove and unload the store from the persistent container. if let store = container.persistentStoreCoordinator.persistentStores.first { try container.persistentStoreCoordinator.remove(store) } } } #endif modelContainer = try ModelContainer(for: vs.AnnotationData.self, vs.GroupData.self, vs.Item.self, vs.Deployment.self, vs.History.self, configurations: config) } catch { fatalError(error.localizedDescription) } } The output is Console Output Where you can see Output Extract Optional arrays with @Relationship are missing, and the entry of record types on cloudkit database container are also missing it. When I attempt to insert an annotation, I got SwiftData/PersistentModel.swift:559: Fatal error: This KeyPath does not appear to relate AnnotationData to anything - \AnnotationData.groups It gets more suspicious when restart the app and try again, the above error end with "AnnotationData.history", and if I tried again the above error end with "AnnotationData.from"... and so on. No matter how my app stop working.
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321
Activity
Jan ’26
How to switch between Core Data Persistent Stores?
What is the best way to switch between Core Data Persistent Stores? My use case is that I have a multi-user app that stores thousands of data items unique to each user. To me, having Persistent Stores for each user seems like the best design to keep their data separate and private. (If anyone believes that storing the data for all users in one Persistent Store is a better design, I'd appreciate hearing from them.) Customers might switch users 5 to 10 times a day. Switching users must be fast, say a second or two at most.
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126
Activity
Jun ’25
How to make a hidden iCloud Container active again?
While experimenting with CloudKit dashboard, I accidentally turned off a iCloud container. Now in the Certificates, Identifiers & Profiles section of developer portal, this iCloud container identifier is listed under "hidden" not "active" I can edit its name but there is not way to unhide or active it again. What am I missing?
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7
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367
Activity
Nov ’25
joblinkapp's registerview problem
我正在使用 Core Data 开发一个 SwiftUI 项目。我的数据模型中有一个名为 AppleUser 的实体,具有以下属性:id (UUID)、name (String)、email (String)、password (String) 和 createdAt (Date)。所有属性都是非可选的。 我使用 Xcode 的自动生成创建了相应的 Core Data 类文件(AppleUser+CoreDataClass.swift 和 AppleUser+CoreDataProperties.swift)。我还有一个 PersistenceController,它使用模型名称 JobLinkModel 初始化 NSPersistentContainer。 当我尝试使用以下方法保存新的 AppleUser 对象时: 让用户 = AppleUser(上下文:viewContext) user.id = UUID() user.name = “用户 1” user.email = “...” user.password = “密码 1” user.createdAt = Date()【电子邮件格式正确,但已替换为“...”出于隐私原因】 尝试?viewContext.save() 我在控制台中收到以下错误:核心数据保存失败:Foundation._GenericObjCError.nilError, [:] 用户快照: [“id”: ..., “name”: “User1”, “email”: “...”, “password”: “...”, “createdAt”: ...] 所有字段都有有效值,核心数据模型似乎正确。我还尝试过: • 检查 NSPersistentContainer(name:) 中的模型名称是否与 .xcdatamodeld 文件 (JobLinkModel) 匹配 • 确保正确设置 AppleUser 实体类、模块和 Codegen(类定义、当前产品模块) • 删除重复或旧的 AppleUser 类文件 • 清理 Xcode 构建文件夹并从模拟器中删除应用程序 • 对上下文使用 @Environment(.managedObjectContext) 尽管如此,在保存新的 AppleUser 对象时,我仍然会收到 _GenericObjCError.nilError。 我想了解: 为什么即使所有字段都不是零且正确分配,核心数据也无法保存? 这可能是由于一些残留的旧类文件引起的,还是我缺少设置中的其他内容? 我应该采取哪些步骤来确保 Core Data 正确识别 AppleUser 实体并允许保存? 任何帮助或指导将不胜感激。
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2
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157
Activity
Sep ’25
Using relationships in SortDescriptor crashing on release
If use a SortDescriptor for a model and sort by some attribute from a relationship, in DEBUG mode it all works fine and sorts. However, in release mode, it is an instant crash. SortDescriptor(.name, order: .reverse) ---- works SortDescriptor(.assignedUser?.name, order: .reverse) ---- works in debug but crash in release. What is the issue here, is it that SwiftData just incompetent to do this?
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131
Activity
Aug ’25
SwiftData: filtering against an array of PersistentIdentifiers
I would like to have a SwiftData predicate that filters against an array of PersistentIdentifiers. A trivial use case could filtering Posts by one or more Categories. This sounds like something that must be trivial to do. When doing the following, however: let categoryIds: [PersistentIdentifier] = categoryFilter.map { $0.id } let pred = #Predicate<Post> { if let catId = $0.category?.persistentModelID { return categoryIds.contains(catId) } else { return false } } The code compiles, but produces the following runtime exception (XCode 26 beta, iOS 26 simulator): 'NSInvalidArgumentException', reason: 'unimplemented SQL generation for predicate : (TERNARY(item != nil, item, nil) IN {}) (bad LHS)' Strangely, the same code works if the array to filter against is an array of a primitive type, e.g. String or Int. What is going wrong here and what could be a possible workaround?
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145
Activity
Jun ’25
Mutating an array of model objects that is a child of a model object
Hi all, In my SwiftUI / SwiftData / Cloudkit app which is a series of lists, I have a model object called Project which contains an array of model objects called subprojects: final class Project1 { var name: String = "" @Relationship(deleteRule: .cascade, inverse: \Subproject.project) var subprojects : [Subproject]? init(name: String) { self.name = name self.subprojects = [] } } The user will select a project from a list, which will generate a list of subprojects in another list, and if they select a subproject, it will generate a list categories and if the user selects a category it will generate another list of child objects owned by category and on and on. This is the pattern in my app, I'm constantly passing arrays of model objects that are the children of other model objects throughout the program, and I need the user to be able to add and remove things from them. My initial approach was to pass these arrays as bindings so that I'd be able to mutate them. This worked for the most part but there were two problems: it was a lot of custom binding code and when I had to unwrap these bindings using init?(_ base: Binding<Value?>), my program would crash if one of these arrays became nil (it's some weird quirk of that init that I don't understand at al). As I'm still learning the framework, I had not realized that the @model macro had automatically made my model objects observable, so I decided to remove the bindings and simply pass the arrays by reference, and while it seems these references will carry the most up to date version of the array, you cannot mutate them unless you have access to the parent and mutate it like such: project.subcategories?.removeAll { $0 == subcategory } project.subcategories?.append(subcategory) This is weirding me out because you can't unwrap subcategories before you try to mutate the array, it has to be done like above. In my code, I like to unwrap all optionals at the moment that I need the values stored in them and if not, I like to post an error to the user. Isn't that the point of optionals? So I don't understand why it's like this and ultimately am wondering if I'm using the correct design pattern for what I'm trying to accomplish or if I'm missing something? Any input would be much appreciated! Also, I do have a small MRE project if the explanation above wasn't clear enough, but I was unable to paste in here (too long), attach the zip or paste a link to Google Drive. Open to sharing it if anyone can tell me the best way to do so. Thanks!
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246
Activity
Sep ’25
Core Data Multiple NSEntityDescriptions claim the NSManagedObject subclass
Hello everyone, I'm trying to adopt the new Staged Migrations for Core Data and I keep running into an error that I haven't been able to resolve. The error messages are as follows: warning: Multiple NSEntityDescriptions claim the NSManagedObject subclass 'Movie' so +entity is unable to disambiguate. warning: 'Movie' (0x60000350d6b0) from NSManagedObjectModel (0x60000213a8a0) claims 'Movie'. error: +[Movie entity] Failed to find a unique match for an NSEntityDescription to a managed object subclass This happens for all of my entities when they are added/fetched. Movie is an abstract entity subclass, and it has the error error: +[Movie entity] Failed to find which is unique to the subclass entities, but this occurs for all entities. The NSPersistentContainer is loaded only once, and I set the following option after it's loaded: storeDescription.setOption( [stages], forKey: NSPersistentStoreStagedMigrationManagerOptionKey ) The warnings and errors only appear after I fetch or save to context. It happens regardless of whether the database was migrated or not. In my test project, using the generic NSManagedObject with NSEntityDescription.insertNewObject(forEntityName: "MyEntity", into: context) does not cause the issue. However, using the generic NSManagedObject is not a viable option for my app. Setting the module to "Current Project Module" doesn't change anything, except that it now prints "claims 'MyModule.Show'" in the warnings. I have verified that there are no other entities with the same name or renameIdentifier. Has anyone else encountered this issue, or can offer any suggestions on how to resolve it? Thanks in advance for any help!
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Activity
4d
NSPersistentCloudKitContainer causes crash on watchOS when device is offline
Hi. I'm hoping someone might be able to help us with an issue that's been affecting our standalone watchOS app for some time now. We've encountered consistent crashes on Apple Watch devices when the app enters the background while the device is offline (i.e., no Bluetooth and no Wi-Fi connection). Through extensive testing, we've isolated the problem to the use of NSPersistentCloudKitContainer. When we switch to NSPersistentContainer, the crashes no longer occur. Interestingly, this issue only affects our watchOS app. The same CloudKit-based persistence setup works reliably on our iOS and macOS apps, even when offline. This leads us to believe the issue may be specific to how NSPersistentCloudKitContainer behaves on watchOS when the device is disconnected from the network. We're targeting watchOS 10 and above. We're unsure if this is a misconfiguration on our end or a potential system-level issue, and we would greatly appreciate any insight or guidance.
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143
Activity
Jun ’25
Core Data, Swift 6, Concurrency and more
I have the following struct doing some simple tasks, running a network request and then saving items to Core Data. Per Xcode 26's new default settings (onisolated(nonsending) & defaultIsolation set to MainActor), the struct and its functions run on the main actor, which works fine and I can even safely omit the context.perform call because of it, which is great. struct DataHandler { func importGames(withIDs ids: [Int]) async throws { ... let context = PersistenceController.shared.container.viewContext for game in games { let newGame = GYGame(context: context) newGame.id = UUID() } try context.save() } } Now, I want to run this in a background thread to increase performance and responsiveness. So I followed this session (https://developer.apple.com/videos/play/wwdc2025/270) and believe the solution is to mark the struct as nonisolated and the function itself as @concurrent. The function now works on a background thread, but I receive a crash: _dispatch_assert_queue_fail. This happens whether I wrap the Core Data calls with context.perform or not. Alongside that I get a few new warnings which I have no idea how to work around. So, what am I doing wrong here? What's the correct way to solve this simple use case with Swift 6's new concurrency stuff and the default main actor isolation in Xcode 26? Curiously enough, when setting onisolated(nonsending) to false & defaultIsolation to non isolating, mimicking the previous behavior, the function works without crashing. nonisolated struct DataHandler { @concurrent func importGames(withIDs ids: [Int]) async throws { ... let context = await PersistenceController.shared.container.newBackgroundContext() for game in games { let newGame = GYGame(context: context) newGame.id = UUID() // Main actor-isolated property 'id' can not be mutated from a nonisolated context; this is an error in the Swift 6 language mode } try context.save() } }
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236
Activity
Jun ’25
defaultIsolation option and Core Data
When creating a new project in Xcode 26, the default for defaultIsolation is MainActor. Core Data creates classes for each entity using code gen, but now those classes are also internally marked as MainActor, which causes issues when accessing managed object from a background thread like this. Is there a way to fix this warning or should Xcode actually mark these auto generated classes as nonisolated to make this better? Filed as FB13840800. nonisolated struct BackgroundDataHandler { @concurrent func saveItem() async throws { let context = await PersistenceController.shared.container.newBackgroundContext() try await context.perform { let newGame = Item(context: context) newGame.timestamp = Date.now // Main actor-isolated property 'timestamp' can not be mutated from a nonisolated context; this is an error in the Swift 6 language mode try context.save() } } } Turning code gen off inside the model and creating it manually, with the nonisolated keyword, gets rid of the warning and still works fine. So I guess the auto generated class could adopt this as well? public import Foundation public import CoreData public typealias ItemCoreDataClassSet = NSSet @objc(Item) nonisolated public class Item: NSManagedObject { }
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Activity
Jun ’25
Invalid bundle ID for container
Hi. I am having this error when trying to write to CloudKit public database. <CKError 0x600000dbc4e0: "Permission Failure" (10/2007); server message = "Invalid bundle ID for container"; On app launch, I check for account status and ensure that the correct bundle identifier and container is being used. When the account status is checked, I do get the correct bundle id and container id printed in the console but trying to read or write to the container would throw that "Invalid bundle ID for container" error. private init() { container = CKContainer.default() publicDB = container.publicCloudDatabase // Check iCloud account status checkAccountStatus() } func checkAccountStatus() { print("🔍 CloudKit Debug:") print("🔍 Bundle identifier from app: (Bundle.main.bundleIdentifier ?? "unknown")") print("🔍 Container identifier: (container.containerIdentifier ?? "unknown")") container.accountStatus { [weak self] status, error in DispatchQueue.main.async { switch status { case .available: self?.isSignedIn = true self?.fetchUserID() case .noAccount, .restricted, .couldNotDetermine: self?.isSignedIn = false self?.errorMessage = "Please sign in to iCloud in Settings to use this app." default: self?.isSignedIn = false self?.errorMessage = "Unknown iCloud account status." } print("User is signed into iCloud: \(self?.isSignedIn ?? false)") print("Account status: \(status.rawValue)") } } } I have tried: Creating a new container Unselecting and selecting the container in signing & capabilities Unselecting and selecting the container in App ID Configuration I used to have swift data models in my code and read that swift data is not compatible with CloudKit public data so I removed all the models and any swift data codes and only uses CloudKit public database. let savedRecord = try await publicDB.save(record) Nothing seems to work. If anyone could help please? Rgds, Hans
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314
Activity
Jun ’25