Swift Concurrency Resources: DevForums tags: Concurrency The Swift Programming Language > Concurrency documentation Migrating to Swift 6 documentation WWDC 2022 Session 110351 Eliminate data races using Swift Concurrency — This ‘sailing on the sea of concurrency’ talk is a great introduction to the fundamentals. WWDC 2021 Session 10134 Explore structured concurrency in Swift — The table that starts rolling out at around 25:45 is really helpful. Swift Async Algorithms package Swift Concurrency Proposal Index DevForum post Why is flow control important? DevForums post Matt Massicotte’s blog Dispatch Resources: DevForums tags: Dispatch Dispatch documentation — Note that the Swift API and C API, while generally aligned, are different in many details. Make sure you select the right language at the top of the page. Dispatch man pages — While the standard Dispatch documentation is good, you can still find some great tidbits in the man pages. See Reading UNIX Manual Pages. Start by reading dispatch in section 3. WWDC 2015 Session 718 Building Responsive and Efficient Apps with GCD [1] WWDC 2017 Session 706 Modernizing Grand Central Dispatch Usage [1] Avoid Dispatch Global Concurrent Queues DevForums post Share and Enjoy — Quinn “The Eskimo!” @ Developer Technical Support @ Apple let myEmail = "eskimo" + "1" + "@" + "apple.com" [1] These videos may or may not be available from Apple. If not, the URL should help you locate other sources of this info.

I have been working on an app for the past few months, and one issue that I have encountered a few times is an error where quick subsequent deletions cause issues with detached tasks that are triggered from some user actions. Inside a Task.detached, I am building an isolated model context, querying for LineItems, then iterating over those items. The crash happens when accessing a Transaction property through a relationship. var byTransactionId: [UUID: [LineItem]] { return Dictionary(grouping: self) { item in item.transaction?.id ?? UUID() } } In this case, the transaction has been deleted, but the relationship existed when the fetch occurred, so the transaction value is non-nil. The crash occurs when accessing the id. This is the error. SwiftData/BackingData.swift:1035: Fatal error: This model instance was invalidated because its backing data could no longer be found the store. PersistentIdentifier(id: SwiftData.PersistentIdentifier.ID(backing: SwiftData.PersistentIdentifier.PersistentIdentifierBacking.managedObjectID(0xb43fea2c4bc3b3f5 <x-coredata://A9EFB8E3-CB47-48B2-A7C4-6EEA25D27E2E/Transaction/p1756>))) I see other posts about this error and am exploring some suggestions, but if anyone has any thoughts, they would be appreciated.

Hey all! in my personal quest to make future proof apps moving to Swift 6, one of my app has a problem when setting an artwork image in MPNowPlayingInfoCenter Here's what I'm using to set the metadata func setMetadata(title: String? = nil, artist: String? = nil, artwork: String? = nil) async throws { let defaultArtwork = UIImage(named: "logo")! var nowPlayingInfo = [ MPMediaItemPropertyTitle: title ?? "***", MPMediaItemPropertyArtist: artist ?? "***", MPMediaItemPropertyArtwork: MPMediaItemArtwork(boundsSize: defaultArtwork.size) { _ in defaultArtwork } ] as [String: Any] if let artwork = artwork { guard let url = URL(string: artwork) else { return } let (data, response) = try await URLSession.shared.data(from: url) guard (response as? HTTPURLResponse)?.statusCode == 200 else { return } guard let image = UIImage(data: data) else { return } nowPlayingInfo[MPMediaItemPropertyArtwork] = MPMediaItemArtwork(boundsSize: image.size) { _ in image } } MPNowPlayingInfoCenter.default().nowPlayingInfo = nowPlayingInfo } the app crashes when hitting MPMediaItemPropertyArtwork: MPMediaItemArtwork(boundsSize: defaultArtwork.size) { _ in defaultArtwork } or nowPlayingInfo[MPMediaItemPropertyArtwork] = MPMediaItemArtwork(boundsSize: image.size) { _ in image } commenting out these two make the app work again. Again, no clue on why. Thanks in advance

In iOS 26, should we have bootloader that runs the repo on startup - or should we have that inside tasks in root view? we have repos that runs as a «closed» functions, we dont throw but updates swiftdata and we use @query in the views. So what is best? and for the repo we should have a repo that runs the upserts manage relations eg? Should that run on a modelactor?

https://developer.apple.com/forums/thread/768776 Swift concurrency is an important part of my day-to-day job. I created the following document for an internal presentation, and I figured that it might be helpful for others. If you have questions or comments, put them in a new thread here on DevForums. Use the App & System Services > Processes & Concurrency topic area and tag it with both Swift and Concurrency. Share and Enjoy — Quinn “The Eskimo!” @ Developer Technical Support @ Apple let myEmail = "eskimo" + "1" + "@" + "apple.com" Swift Concurrency Proposal Index This post summarises the Swift Evolution proposals that went into the Swift concurrency design. It covers the proposal that are implemented in Swift 6.2, plus a few additional ones that aren’t currently available. The focus is here is the Swift Evolution proposals. For general information about Swift concurrency, see the documentation referenced by Concurrency Resources. Swift 6.0 The following Swift Evolution proposals form the basis of the Swift 6.0 concurrency design. SE-0176 Enforce Exclusive Access to Memory link: SE-0176 notes: This defines the “Law of Exclusivity”, a critical foundation for both serial and concurrent code. SE-0282 Clarify the Swift memory consistency model ⚛︎ link: SE-0282 notes: This defines Swift’s memory model, that is, the rules about what is and isn’t allowed when it comes to concurrent memory access. SE-0296 Async/await link: SE-0296 introduces: async functions, async, await SE-0297 Concurrency Interoperability with Objective-C link: SE-0297 notes: Specifies how Swift imports an Objective-C method with a completion handler as an async method. Explicitly allows @objc actors. SE-0298 Async/Await: Sequences link: SE-0298 introduces: AsyncSequence, for await syntax notes: This just defines the AsyncSequence protocol. For one concrete implementation of that protocol, see SE-0314. SE-0300 Continuations for interfacing async tasks with synchronous code link: SE-0300 introduces: CheckedContinuation, UnsafeContinuation notes: Use these to create an async function that wraps a legacy request-reply concurrency construct. SE-0302 Sendable and @Sendable closures link: SE-0302 introduces: Sendable, @Sendable closures, marker protocols SE-0304 Structured concurrency link: SE-0304 introduces: unstructured and structured concurrency, Task, cancellation, CancellationError, withTaskCancellationHandler(…), sleep(…), withTaskGroup(…), withThrowingTaskGroup(…) notes: For the async let syntax, see SE-0317. For more ways to sleep, see SE-0329 and SE-0374. For discarding task groups, see SE-0381. SE-0306 Actors link: SE-0306 introduces: actor syntax notes: For actor-isolated parameters and the nonisolated keyword, see SE-0313. For global actors, see SE-0316. For custom executors and the Actor protocol, see SE-0392. SE-0311 Task Local Values link: SE-0311 introduces: TaskLocal SE-0313 Improved control over actor isolation link: SE-0313 introduces: isolated parameters, nonisolated SE-0314 AsyncStream and AsyncThrowingStream link: SE-0314 introduces: AsyncStream, AsyncThrowingStream, onTermination notes: These are super helpful when you need to publish a legacy notification construct as an async stream. For a simpler API to create a stream, see SE-0388. SE-0316 Global actors link: SE-0316 introduces: GlobalActor, MainActor notes: This includes the @MainActor syntax for closures. SE-0317 async let bindings link: SE-0317 introduces: async let syntax SE-0323 Asynchronous Main Semantics link: SE-0323 SE-0327 On Actors and Initialization link: SE-0327 notes: For a proposal to allow access to non-sendable isolated state in a deinitialiser, see SE-0371. SE-0329 Clock, Instant, and Duration link: SE-0329 introduces: Clock, InstantProtocol, DurationProtocol, Duration, ContinuousClock, SuspendingClock notes: For another way to sleep, see SE-0374. SE-0331 Remove Sendable conformance from unsafe pointer types link: SE-0331 SE-0337 Incremental migration to concurrency checking link: SE-0337 introduces: @preconcurrency, explicit unavailability of Sendable notes: This introduces @preconcurrency on declarations, on imports, and on Sendable protocols. For @preconcurrency conformances, see SE-0423. SE-0338 Clarify the Execution of Non-Actor-Isolated Async Functions link: SE-0338 note: This change has caught a bunch of folks by surprise and there’s a discussion underway as to whether to adjust it. SE-0340 Unavailable From Async Attribute link: SE-0340 introduces: noasync availability kind SE-0343 Concurrency in Top-level Code link: SE-0343 notes: For how strict concurrency applies to global variables, see SE-0412. SE-0374 Add sleep(for:) to Clock link: SE-0374 notes: This builds on SE-0329. SE-0381 DiscardingTaskGroups link: SE-0381 introduces: DiscardingTaskGroup, ThrowingDiscardingTaskGroup notes: Use this for task groups that can run indefinitely, for example, a network server. SE-0388 Convenience Async[Throwing]Stream.makeStream methods link: SE-0388 notes: This builds on SE-0314. SE-0392 Custom Actor Executors link: SE-0392 introduces: Actor protocol, Executor, SerialExecutor, ExecutorJob, assumeIsolated(…) notes: For task executors, a closely related concept, see SE-0417. For custom isolation checking, see SE-0424. SE-0395 Observation link: SE-0395 introduces: Observation module, Observable notes: While this isn’t directly related to concurrency, it’s relationship to Combine, which is an important exising concurrency construct, means I’ve included it in this list. SE-0401 Remove Actor Isolation Inference caused by Property Wrappers link: SE-0401, commentary availability: upcoming feature flag: DisableOutwardActorInference SE-0410 Low-Level Atomic Operations ⚛︎ link: SE-0410 introduces: Synchronization module, Atomic, AtomicLazyReference, WordPair SE-0411 Isolated default value expressions link: SE-0411, commentary SE-0412 Strict concurrency for global variables link: SE-0412 introduces: nonisolated(unsafe) notes: While this is a proposal about globals, the introduction of nonisolated(unsafe) applies to “any form of storage”. SE-0414 Region based Isolation link: SE-0414, commentary notes: To send parameters and results across isolation regions, see SE-0430. SE-0417 Task Executor Preference link: SE-0417, commentary introduces: withTaskExecutorPreference(…), TaskExecutor, globalConcurrentExecutor notes: This is closely related to the custom actor executors defined in SE-0392. SE-0418 Inferring Sendable for methods and key path literals link: SE-0418, commentary availability: upcoming feature flag: InferSendableFromCaptures notes: The methods part of this is for “partial and unapplied methods”. SE-0420 Inheritance of actor isolation link: SE-0420, commentary introduces: #isolation, optional isolated parameters notes: This is what makes it possible to iterate over an async stream in an isolated async function. SE-0421 Generalize effect polymorphism for AsyncSequence and AsyncIteratorProtocol link: SE-0421, commentary notes: Previously AsyncSequence used an experimental mechanism to support throwing and non-throwing sequences. This moves it off that. Instead, it uses an extra Failure generic parameter and typed throws to achieve the same result. This allows it to finally support a primary associated type. Yay! SE-0423 Dynamic actor isolation enforcement from non-strict-concurrency contexts link: SE-0423, commentary introduces: @preconcurrency conformance notes: This adds a number of dynamic actor isolation checks (think assumeIsolated(…)) to close strict concurrency holes that arise when you interact with legacy code. SE-0424 Custom isolation checking for SerialExecutor link: SE-0424, commentary introduces: checkIsolation() notes: This extends the custom actor executors introduced in SE-0392 to support isolation checking. SE-0430 sending parameter and result values link: SE-0430, commentary introduces: sending notes: Adds the ability to send parameters and results between the isolation regions introduced by SE-0414. SE-0431 @isolated(any) Function Types link: SE-0431, commentary, commentary introduces: @isolated(any) attribute on function types, isolation property of functions values notes: This is laying the groundwork for SE-NNNN Closure isolation control. That, in turn, aims to bring the currently experimental @_inheritActorContext attribute into the language officially. SE-0433 Synchronous Mutual Exclusion Lock 🔒 link: SE-0433 introduces: Mutex SE-0434 Usability of global-actor-isolated types link: SE-0434, commentary availability: upcoming feature flag: GlobalActorIsolatedTypesUsability notes: This loosen strict concurrency checking in a number of subtle ways. Swift 6.1 Swift 6.1 has the following additions. Vision: Improving the approachability of data-race safety link: vision SE-0442 Allow TaskGroup’s ChildTaskResult Type To Be Inferred link: SE-0442, commentary notes: This represents a small quality of life improvement for withTaskGroup(…) and withThrowingTaskGroup(…). SE-0449 Allow nonisolated to prevent global actor inference link: SE-0449, commentary notes: This is a straightforward extension to the number of places you can apply nonisolated. Swift 6.2 Xcode 26 beta has two new build settings: Approachable Concurrency enables the following feature flags: DisableOutwardActorInference, GlobalActorIsolatedTypesUsability, InferIsolatedConformances, InferSendableFromCaptures, and NonisolatedNonsendingByDefault. Default Actor Isolation controls SE-0466 Swift 6.2, still in beta, has the following additions. SE-0371 Isolated synchronous deinit link: SE-0371, commentary introduces: isolated deinit notes: Allows a deinitialiser to access non-sendable isolated state, lifting a restriction imposed by SE-0327. SE-0457 Expose attosecond representation of Duration link: SE-0457 introduces: attoseconds, init(attoseconds:) SE-0461 Run nonisolated async functions on the caller’s actor by default link: SE-0461 availability: upcoming feature flag: NonisolatedNonsendingByDefault introduces: nonisolated(nonsending), @concurrent notes: This represents a significant change to how Swift handles actor isolation by default, and introduces syntax to override that default. SE-0462 Task Priority Escalation APIs link: SE-0462 introduces: withTaskPriorityEscalationHandler(…) notes: Code that uses structured concurrency benefits from priority boosts automatically. This proposal exposes APIs so that code using unstructured concurrency can do the same. SE-0463 Import Objective-C completion handler parameters as @Sendable link: SE-0463 notes: This is a welcome resolution to a source of much confusion. SE-0466 Control default actor isolation inference link: SE-0466, commentary availability: not officially approved, but a de facto part of Swift 6.2 introduces: -default-isolation compiler flag notes: This is a major component of the above-mentioned vision document. SE-0468 Hashable conformance for Async(Throwing)Stream.Continuation link: SE-0468 notes: This is an obvious benefit when you’re juggling a bunch of different async streams. SE-0469 Task Naming link: SE-0469 introduces: name, init(name:…) SE-0470 Global-actor isolated conformances link: SE-0470 availability: upcoming feature flag: InferIsolatedConformances introduces: @SomeActor protocol conformance notes: This is particularly useful when you want to conform an @MainActor type to Equatable, Hashable, and so on. SE-0471 Improved Custom SerialExecutor isolation checking for Concurrency Runtime link: SE-0471 notes: This is a welcome extension to SE-0424. SE-0472 Starting tasks synchronously from caller context link: SE-0472 introduces: immediate[Detached](…), addImmediateTask[UnlessCancelled](…), notes: This introduces the concept of an immediate task, one that initially uses the calling execution context. This is one of those things where, when you need it, you really need it. But it’s hard to summary when you might need it, so you’ll just have to read the proposal (-: In Progress The proposals in this section didn’t make Swift 6.2. SE-0406 Backpressure support for AsyncStream link: SE-0406 availability: returned for revision notes: Currently AsyncStream has very limited buffering options. This was a proposal to improve that. This feature is still very much needed, but the outlook for this proposal is hazy. My best guess is that something like this will land first in the Swift Async Algorithms package. See this thread. SE-NNNN Closure isolation control link: SE-NNNN introduces: @inheritsIsolation availability: not yet approved notes: This aims to bring the currently experimental @_inheritActorContext attribute into the language officially. It’s not clear how this will play out given the changes in SE-0461. Revision History 2025-09-02 Updated for the upcoming release Swift 6.2. 2025-04-07 Updated for the release of Swift 6.1, including a number of things that are still in progress. 2024-11-09 First post.

Hi, In the WWDC25 session Elevate an app with Swift concurrency (timestamps: 8:04 and later), the StickerViewModel is shown annotated with @Observable but not @MainActor. The narration mentions that updates happen on the main thread, but that guarantee is left implicit in the calling code. In Swift 6, though, one of the major benefits is stronger compiler enforcement against data races and isolation rules. If a view model were also annotated with @MainActor, then the compiler could enforce that observable state is only updated on the main actor, preventing accidental background mutations or updates that can cause data races between nonisolated and main actor-isolated uses. Since @Observable already signals that state changes are intended to be observed (and in practice, usually by views), it seems natural that such types should also be main-actor isolated. Otherwise, we’re left with an implicit expectation that updates will always come from the main thread, but without the compiler’s help in enforcing that rule. This also ties into the concept of local reasoning that was emphasized in other Swift 6 talks (e.g. Beyond the basics of structured concurrency). With @MainActor, I can look at a view model and immediately know that all of its state is main-actor isolated. With only @Observable, that guarantee is left out, which feels like it weakens the clarity that Swift 6 is trying to promote. Would it be considered a best practice in Swift 6 to use both @Observable and @MainActor for UI-facing view models? Or is the intention that SwiftUI developers should rely on calling context to ensure main-thread updates, even if that means the compiler cannot enforce isolation? Thanks!

Hi, Are there rules around using Foundation Models: In a background task/session? Concurrently, i.e. a bunch simultaneously using Swift Concurrency? I couldn't find this in the docs (sorry if I missed it) so wondering what's supported and what the best practice is here. In case it matters, my primary platform is Vision Pro (so, M2).

I filed the following issue on swiftlang/swift on GitHub (Aug 8th), and a followup the swift.org forums, but not getting any replies. As we near the release of Swift 6.2, I want to know if what I'm seeing below is expected, or if it's another case where the compiler needs a fix. protocol P1: Equatable { } struct S1: P1 { } // Error: Conformance of 'S1' to protocol 'P1' crosses into main actor-isolated code an can cause data races struct S1Workaround: @MainActor P1 { } // OK // Another potential workaround if `Equatable` conformance can be moved to the conforming type. protocol P2 { } struct S2: Equatable, P2 { } // OK There was a prior compiler bug fix which addressed inhereted protocols regarding @MainActor. For Equatable, one still has to use @MainActoreven when the default actor isolation is MainActor. Also affects Hashable and any other protocol inheriting from Equatable.

Hello, While watching WWDC25: Code-along: Elevate an app with Swift concurrency at timestamp 25:48, I noticed something in the slide/diagram that might be incorrect. The diagram shows ExtractSticker twice, but based on the code context and spoken explanation, I think it was meant to be ExtractSticker and ExtractColor. Reasoning: The surrounding code and narration describe the use of async let and a Sendable Data object. From the flow, one task extracts a sticker while the other extracts a color, so it seems like the diagram is inconsistent. I do understand that with @concurrent, having two ExtractSticker operations on the same Data is technically possible (with two concurrent process executing their respective ExtractSticker) — but that would be a different meaning than what the talk was describing. Since concurrency is already a subtle and error-prone topic, I thought it was worth pointing this out. If I’m mistaken, I’d love clarification. Otherwise, this could be a small correction to keep things aligned and clearer for everyone. Minor point overall, but Swift 6’s concurrency model is doing a fantastic job at helping us write safer code—so thank you to the team for that! (Attaching screenshots for reference)

I have a UIKit app where I've adopted SwiftData and I'm struggling with a crash coming in from some of my users. I'm not able to reproduce it myself and as it only happens to a small fraction of my user base, it seems like a race condition of some sort. This is the assertion message: SwiftData/DefaultStore.swift:453: Fatal error: API Contract Violation: Editors must register their identifiers before invoking operations on this store SwiftData.DefaultStore: 00CF060A-291A-4E79-BEC3-E6A6B20F345E did not. (ID is unique per crash) This is the ModelActor that crashes: @available(iOS 17, *) @ModelActor actor ConsumptionDatabaseStorage: ConsumptionSessionStorage { struct Error: LocalizedError { var errorDescription: String? } private let sortDescriptor = [SortDescriptor(\SDConsumptionSession.startTimeUtc, order: .reverse)] static func createStorage(userId: String) throws -> ConsumptionDatabaseStorage { guard let appGroupContainer = FileManager.default.containerURL(forSecurityApplicationGroupIdentifier: UserDefaults.defaultAppGroupIdentifier) else { throw Error(errorDescription: "Invalid app group container ID") } func createModelContainer(databaseUrl: URL) throws -> ModelContainer { return try ModelContainer(for: SDConsumptionSession.self, SDPriceSegment.self, configurations: ModelConfiguration(url: databaseUrl)) } let databaseUrl = appGroupContainer.appendingPathComponent("\(userId).sqlite") do { return self.init(modelContainer: try createModelContainer(databaseUrl: databaseUrl)) } catch { // Creating the model storage failed. Remove the database file and try again. try? FileManager.default.removeItem(at: databaseUrl) return self.init(modelContainer: try createModelContainer(databaseUrl: databaseUrl)) } } func isStorageEmpty() async -> Bool { (try? self.modelContext.fetchCount(FetchDescriptor<SDConsumptionSession>())) ?? 0 == 0 // <-- Crash here! } func sessionsIn(interval: DateInterval) async throws -> [ConsumptionSession] { let fetchDescriptor = FetchDescriptor(predicate: #Predicate<SDConsumptionSession> { sdSession in if let startDate = sdSession.startTimeUtc { return interval.start <= startDate && interval.end > startDate } else { return false } }, sortBy: self.sortDescriptor) let consumptionSessions = try self.modelContext.fetch(fetchDescriptor) // <-- Crash here! return consumptionSessions.map { ConsumptionSession(swiftDataSession: $0) } } func updateSessions(sessions: [ConsumptionSession]) async throws { if #unavailable(iOS 18) { // Price segments are duplicated if re-inserted so unfortunately we have to delete and reinsert sessions. // On iOS 18, this is enforced by the #Unique macro on SDPriceSegment. let sessionIds = Set(sessions.map(\.id)) try self.modelContext.delete(model: SDConsumptionSession.self, where: #Predicate<SDConsumptionSession> { sessionIds.contains($0.id) }) } for session in sessions { self.modelContext.insert(SDConsumptionSession(consumptionSession: session)) } if self.modelContext.hasChanges { try self.modelContext.save() } } func deleteAllSessions() async { if #available(iOS 18, *) { try? self.modelContainer.erase() } else { self.modelContainer.deleteAllData() } } } The actor conforms to this protocol: protocol ConsumptionSessionStorage { func isStorageEmpty() async -> Bool func hasCreditCardSessions() async -> Bool func sessionsIn(interval: DateInterval) async throws -> [ConsumptionSession] func updateSessions(sessions: [ConsumptionSession]) async throws func deleteAllSessions() async } The crash is coming in from line 30 and 41, in other words, when trying to fetch data from the database. There doesn't seem to be any common trait for the crashes. They occur across iOS versions and device types. Any idea what might cause this?

I have some code which handles doing some computation on a background thread before updating Core Data NSManagedObjects by using the NSManagedObjectContext.perform functions. This code is covered in Sendable warnings in Xcode 26 (beta 6) because my NSManagedObject subclasses (autogenerated) are non-Sendable and NSManagedObjectContext.perform function takes a Sendable closure. But I can't really figure out what I should be doing. I realize this pattern is non-ideal for Swift concurrency, but it's what Core Data demands AFAIK. How do I deal with this? let moc = object.managedObjectContext! try await moc.perform { object.completed = true // Capture of 'object' with non-Sendable type 'MySpecialObject' in a '@Sendable' closure try moc.save() } Thanks in advance for your help!

I'm working with SwiftData and SwiftUI and it's not clear to me if it is good practice to have a @ModelActor directly populate a SwiftUI view. For example when having to combine manual lab results and clinial results from HealthKit. The Clinical lab results are an async operation: @ModelActor actor LabResultsManager { func fetchLabResultsWithHealthKit() async throws -> [LabResultDto] { let manualEntries = try modelContext.fetch(FetchDescriptor<LabResult>()) let clinicalLabs = (try? await HealthKitService.getLabResults()) ?? [] return (manualEntries + clinicalLabs).sorted { $0.date > $1.date }.map { return LabResultDto(from: $0) } } } struct ContentView: View { @State private var labResults: [LabResultDto] = [] var body: some View { List(labResults, id: \.id) { result in VStack(alignment: .leading) { Text(result.testName) Text(result.date, style: .date) } } .task { do { let labManager = LabResultsManager() labResults = try await labManager.fetchLabResultsWithHealthKit() } catch { // Handle error } } } } EDIT: I have a few views that would want to use these labResults so I need an implementation that can be reused. Having to fetch and combine in each view will not be good practice. Can I pass a modelContext to a viewModel?

I have a TVTopShelfContentProvider that implements func loadTopShelfContent() async -&gt; (any TVTopShelfContent)? When running on Xcode 26 b5 I am seeing the following error in swift 6 mode. Non-Sendable type '(any TVTopShelfContent)?' cannot be returned from nonisolated override to caller of superclass instance method 'loadTopShelfContent()' I'm not sure exactly what's changed here as it used to compile just fine but it's unclear now how I can work-around this error or how the API is supposed to be used. The following definition is enough to trigger the error in Swift 6 language mode. import TVServices class ContentProvider: TVTopShelfContentProvider { override func loadTopShelfContent() async -&gt; (any TVTopShelfContent)? { return nil } } I can "fix" it by adding @preconcurrency to the TVServices import but it seems like this API is unusable currently? Or maybe it's user error on my part?

I'm struggling to convert Swift 5 to Swift 6. As advised in doc, I first turned strict concurrency ON. I got no error. Then, selected swift6… and problems pop up. I have a UIViewController with IBOutlets: eg a TextField. computed var eg duree func using UNNotification: func userNotificationCenter I get the following error in the declaration line of the func userNotificationCenter: Main actor-isolated instance method 'userNotificationCenter(_:didReceive:withCompletionHandler:)' cannot be used to satisfy nonisolated requirement from protocol 'UNUserNotificationCenterDelegate' So, I declared the func as non isolated. This func calls another func func2, which I had also to declare non isolated. Then I get error on the computed var used in func2 Main actor-isolated property 'duree' can not be referenced from a nonisolated context So I declared duree as nonsilated(unsafe). Now comes the tricky part. The computed var references the IBOutlet dureeField if dureeField.text == "X" leading to the error Main actor-isolated property 'dureeField' can not be referenced from a nonisolated context So I finally declared the class as mainActor and the textField as nonisolated @IBOutlet nonisolated(unsafe) weak var dureeField : UITextField! That silences the error (but declaring unsafe means I get no extra robustness with swift6) just to create a new one when calling dureeField.text: Main actor-isolated property 'text' can not be referenced from a nonisolated context Question: how to address properties inside IBOutlets ? I do not see how to declare them non isolated and having to do it on each property of each IBOutlet would be impracticable. The following did work, but will make code very verbose: if MainActor.assumeIsolated({dureeField.text == "X"}) { So I must be missing something.

When attempting to compile an existing project with Swift 6, default isolation set to MainActor and approachable concurrency enabled, all awakeFromNib functions lead to the following compile error: "Main actor-isolated instance method 'awakeFromNib()' has different actor isolation from nonisolated overridden declaration" I've seen articles before approachable concurrency stating that one remedy is to wrap code within the function with MainActor.assumeIsolated{ }. However, that no longer addresses the error. One combination of changes that removes the error is doing the following: nonisolated override func awakeFromNib() { super.awakeFromNib() MainActor.assumeIsolated { ... } } Honestly, that's a mess. Long term, we are looking to remove all these functions, but does anyone have a better solution?

I'm running into a weird SwiftUI concurrency issue that only seems to happen on a real device (iOS 18.5 in my case), and not in simulator. I have a NavigationSplitView where the Detail view uses .task(id:_:) to perform some async work upon appearance (in my real-world case, a map snapshot). When running this on a real device, the first execution of the task works as expected. However, any task subsequent executions, even ones for the same id, always start in the Task.isCancelled state. Is there something about .task(id:_:) that I'm misunderstanding, or have I stumbled upon a serious bug here? import SwiftUI struct ContentView: View { var body: some View { TaskBugSplitView() } } struct TestItem: Identifiable, Hashable { var id: Int var name: String } struct TaskBugSplitView: View { @State private var selectedItemIndex: [TestItem].Index? @State private var testItems: [TestItem] = [ TestItem(id: 1, name: "First Item"), TestItem(id: 2, name: "Second Item"), TestItem(id: 3, name: "Third Item"), TestItem(id: 4, name: "Fourth Item"), TestItem(id: 5, name: "Fifth Item") ] var body: some View { NavigationSplitView { List(testItems.indices, id: \.self, selection: $selectedItemIndex) { item in Text(testItems[item].name) } } detail: { if let selectedItemIndex { TaskBugDetailView(item: testItems[selectedItemIndex]) } else { Text("Select an item") .foregroundStyle(.secondary) } } } } struct TaskBugDetailView: View { @State var item: TestItem @State private var taskResult = "Not started" var body: some View { VStack(spacing: 20) { Text("Item: \(item.name)") .font(.title2) Text("Task Result:") .font(.headline) Text(taskResult) .foregroundStyle(taskResult.contains("CANCELLED") ? .red : .primary) Spacer() } .padding() .navigationTitle(item.name) .task(id: item.id) { // BUG: On real devices, Task.isCancelled is true immediately for all tasks // after the first successful one, even though the ID has changed if Task.isCancelled { taskResult = "CANCELLED at start" print("Task cancelled at start for item \(item.id)") return } taskResult = "SUCCESS" print("Task completed successfully for item \(item.id)") } } }

AVAudioFormat has no Swift concurrency annotations but the documentation states "Instances of this class are immutable." This made me always assume it was safe to pass AVAudioFormat instances around. Is this the case? If so can it be marked as Sendable? Am I missing something?

Hi! I configure proxy for webview like DispatchQueue.main.async { self.webView.configuration.websiteDataStore.proxyConfigurations = [proxyConfiguration] } It is fine in iosiOS 17 however, it crashes in iOS 18.3. And the problem seems to be related to the left side of the equation. I tried to call print(self.webView.configuration.websiteDataStore.proxyConfigurations.count) in async block and got the same bad access error. But if stop at that line of code and call po self.webView.configuration.websiteDataStore.proxyConfigurations in debugger it returns 0 elements. Did anyone have the same problem? What may cause the exception?

Every time macOS goes to sleep the processes get suspended which is expected. But during the sleep period, all processes keep coming back and they all get a small execution window where they make some n/w requests. Regardless of what power settings i have. It also does not matter whether my app is a daemon or not Is there any way that i can disable this so that when system is in sleep, it stays in suspended, no intermittent execution window? I have tried disabling Wake for network access setting but processes still keep getting intermittent execution window. Is there any way that i can prevent my app from coming back while in sleep. I don't want my app to get execution window, perform some executions and then get suspended not knowing when it will get execution window again?

In my Xcode app, I was attempting to use the #Playground macro to play around with some of the Foundation Model features to see if they would work for my iOS app. However, every time I used a #Playground macro, even if it was empty, it would receive the following error: /var/folders/q2/x5b9x0y161bb2l_0yj1_j6wm0000gn/T/swift-generated-sources/@__swiftmacro_20PlaygroundMacroIssue0022ContentViewswift_tiAIefMX26_0_33_B691877350F20F2DFC040B9E585F4D10Ll0A0fMf_.swift:51:5 Main actor-isolated let '$s20PlaygroundMacroIssue0022ContentViewswift_tiAIefMX26_0_33_B691877350F20F2DFC040B9E585F4D10Ll0A0fMf_23PlaygroundContentRecordfMu_' can not be referenced from a nonisolated context Here are my Xcode and system versions: Mac is running the first public beta of Tahoe. iOS Simulator is running 26.0 dev beta 4. Xcode is Xcode 26 beta 4. So, I went to try to reproduce the error in a blank iOS app project (the error above is the one that I reproduced in that project). Here are the steps that I took. I created a new iOS project in Xcode 26. I went into the ContentView.swift that was created for me and imported the Playgrounds module and created a blank #Playground at the bottom of the file. I then compiled the project and it ran just fine. To try to find out what the issue was, I looked at the concurrency settings. In my real app, Strict Concurrency Checking was set to Complete but was Minimal in my test project. So I went and changed that setting in my real app and it didn't fix anything. Next, I looked at the Swift Version, which turned out to be the culprit. My test app was running Swift 5 whereas the real app was running Swift 6. It seems to have crashed while running Swift 6, not 5. I have trouble understanding what the error is saying. I have tried using the Code Intelligence feature to fix the bug but it hasn't helped. Has anyone here experienced a similar bug? Is there something I can do to fix it or is this an error in Xcode that should be reported? I have attached an iCloud link to my test project if anybody wants to see if they can reproduce the issue: here Thanks!

Hello, We have been encountering a persistent crash in our application, which is deployed exclusively on iPad devices. The crash occurs in the following code block: let requestHandler = ImageRequestHandler(paddedImage) var request = CoreMLRequest(model: model) request.cropAndScaleAction = .scaleToFit let results = try await requestHandler.perform(request) The client using this code is wrapped inside an actor, following Swift concurrency principles. The issue has been consistently reproduced across multiple iPadOS versions, including: iPad OS - 18.4.0 iPad OS - 18.4.1 iPad OS - 18.5.0 This is the crash log - Crashed: com.apple.VN.detectorSyncTasksQueue.VNCoreMLTransformer 0 libobjc.A.dylib 0x7b98 objc_retain + 16 1 libobjc.A.dylib 0x7b98 objc_retain_x0 + 16 2 libobjc.A.dylib 0xbf18 objc_getProperty + 100 3 Vision 0x326300 -[VNCoreMLModel predictWithCVPixelBuffer:options:error:] + 148 4 Vision 0x3273b0 -[VNCoreMLTransformer processRegionOfInterest:croppedPixelBuffer:options:qosClass:warningRecorder:error:progressHandler:] + 748 5 Vision 0x2ccdcc __119-[VNDetector internalProcessUsingQualityOfServiceClass:options:regionOfInterest:warningRecorder:error:progressHandler:]_block_invoke_5 + 132 6 Vision 0x14600 VNExecuteBlock + 80 7 Vision 0x14580 __76+[VNDetector runSuccessReportingBlockSynchronously:detector:qosClass:error:]_block_invoke + 56 8 libdispatch.dylib 0x6c98 _dispatch_block_sync_invoke + 240 9 libdispatch.dylib 0x1b584 _dispatch_client_callout + 16 10 libdispatch.dylib 0x11728 _dispatch_lane_barrier_sync_invoke_and_complete + 56 11 libdispatch.dylib 0x7fac _dispatch_sync_block_with_privdata + 452 12 Vision 0x14110 -[VNControlledCapacityTasksQueue dispatchSyncByPreservingQueueCapacity:] + 60 13 Vision 0x13ffc +[VNDetector runSuccessReportingBlockSynchronously:detector:qosClass:error:] + 324 14 Vision 0x2ccc80 __119-[VNDetector internalProcessUsingQualityOfServiceClass:options:regionOfInterest:warningRecorder:error:progressHandler:]_block_invoke_4 + 336 15 Vision 0x14600 VNExecuteBlock + 80 16 Vision 0x2cc98c __119-[VNDetector internalProcessUsingQualityOfServiceClass:options:regionOfInterest:warningRecorder:error:progressHandler:]_block_invoke_3 + 256 17 libdispatch.dylib 0x1b584 _dispatch_client_callout + 16 18 libdispatch.dylib 0x6ab0 _dispatch_block_invoke_direct + 284 19 Vision 0x2cc454 -[VNDetector internalProcessUsingQualityOfServiceClass:options:regionOfInterest:warningRecorder:error:progressHandler:] + 632 20 Vision 0x2cd14c __111-[VNDetector processUsingQualityOfServiceClass:options:regionOfInterest:warningRecorder:error:progressHandler:]_block_invoke + 124 21 Vision 0x14600 VNExecuteBlock + 80 22 Vision 0x2ccfbc -[VNDetector processUsingQualityOfServiceClass:options:regionOfInterest:warningRecorder:error:progressHandler:] + 340 23 Vision 0x125410 __swift_memcpy112_8 + 4852 24 libswift_Concurrency.dylib 0x5c134 swift::runJobInEstablishedExecutorContext(swift::Job*) + 292 25 libswift_Concurrency.dylib 0x5d5c8 swift_job_runImpl(swift::Job*, swift::SerialExecutorRef) + 156 26 libdispatch.dylib 0x13db0 _dispatch_root_queue_drain + 364 27 libdispatch.dylib 0x1454c _dispatch_worker_thread2 + 156 28 libsystem_pthread.dylib 0x9d0 _pthread_wqthread + 232 29 libsystem_pthread.dylib 0xaac start_wqthread + 8 We found an issue similar to us - https://developer.apple.com/forums/thread/770771. But the crash logs are quite different, we believe this warrants further investigation to better understand the root cause and potential mitigation strategies. Please let us know if any additional information would help diagnose this issue.