Considering below dummy codes: @MainActor var globalNumber = 0 @MainActor func increase(_ number: inout Int) async { // some async code excluded number += 1 } class Dummy: @unchecked Sendable { @MainActor var number: Int { get { globalNumber } set { globalNumber = newValue } } @MainActor func change() async { await increase(&number) //Actor-isolated property 'number' cannot be passed 'inout' to 'async' function call } } I'm not really trying to make an increasing function like that, this is just an example to make everything happen. As for why number is a computed property, this is to trigger the actor-isolated condition (otherwise, if the property is stored and is a value type, this condition will not be triggered). Under these conditions, in function change(), I got the error: Actor-isolated property 'number' cannot be passed 'inout' to 'async' function call. My question is: Why Actor-isolated property cannot be passed 'inout' to 'async' function call? What is the purpose of this design? If this were allowed, what problems might it cause?

Are there any plans to add RBI support (the sending keyword) to the OSAllocatedLock interface? So it could be used with non-sendable objects without surrendering to the unchecked API

I've got a problem with compatibility with Swift6 in iOS app that I have no idea how to sort it out. That is an extract from my main app file @MainActor @main struct LangpadApp: App { ... @State private var notificationDataProvider = NotificationDataProvider() @UIApplicationDelegateAdaptor(NotificationServiceDelegate.self) var notificationServiceDelegate var body: some Scene { WindowGroup { TabView(selection: $tabSelection) { ... } .onChange(of: notificationDataProvider.dateId) { oldValue, newValue in if !notificationDataProvider.dateId.isEmpty { tabSelection = 4 } } } } init() { notificationServiceDelegate.notificationDataProvider = notificationDataProvider } } and the following code shows other classes @MainActor final class NotificationServiceDelegate: UIResponder, UIApplicationDelegate, UNUserNotificationCenterDelegate { var notificationDataProvider: NotificationDataProvider? func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey : Any]? = nil) -> Bool { UNUserNotificationCenter.current().delegate = self return true } func setDateId(dateId: String) { if let notificationDataProvider = notificationDataProvider { notificationDataProvider.dateId = dateId } } nonisolated func userNotificationCenter(_ center: UNUserNotificationCenter, didReceive response: UNNotificationResponse) async { // After user pressed notification let content = response.notification.request.content if let dateId = content.userInfo["dateId"] as? String { await MainActor.run { setDateId(dateId: dateId) } } } nonisolated func userNotificationCenter(_ center: UNUserNotificationCenter, willPresent notification: UNNotification) async -> UNNotificationPresentationOptions { // Before notification is to be shown return [.sound, .badge, .banner, .list] } } @Observable final public class NotificationDataProvider : Sendable { public var dateId = "" } I have set Strict Concurrency Checking to 'Complete.' The issue I'm facing is related to the delegate class method, which is invoked after the user presses the notification. Current state causes crash after pressing notification. If I remove "nonisolated" keyword it works fine but I get the following warning Non-sendable type 'UNNotificationResponse' in parameter of the protocol requirement satisfied by main actor-isolated instance method 'userNotificationCenter(_:didReceive:)' cannot cross actor boundary; this is an error in the Swift 6 language mode I have no idea how to make it Swift6 compatible. Does anyone have any clues?

In the header for UIViewController, the method dismissViewControllerAnimated is declared like this: - (void)dismissViewControllerAnimated: (BOOL)flag completion: (void (^ __nullable)(void))completion NS_SWIFT_DISABLE_ASYNC API_AVAILABLE(ios(5.0)); NS_SWIFT_DISABLE_ASYNC means that there's no async version exposed like there would normally be of a method that exposes a completion handler. Why is this? And is it unwise / unsafe for me to make my own async version of it using a continuation? My use case is that I want a method that will sequentially dismiss all view controllers presented by a root view controller. So I could have this extension on UIViewController: extension UIViewController { func dismissAsync(animated: Bool) async { await withCheckedContinuation { continuation in self.dismiss(animated: animated) { continuation.resume() } } } func dismissPresentedViewControllers() async { while self.topPresentedViewController != self { await self.topPresentedViewController.dismissAsync(animated: true) } } var topPresentedViewController: UIViewController { var result = self while result.presentedViewController != nil { result = result.presentedViewController! } return result }

I found a similar problem here https://developer.apple.com/forums/thread/764777 and I could solve my problem by wrapping the call to requestAutomaticPassPresentationSuppression in a call to DispatchQueue.global().async. But my question is if this is really how things should work. Even with strict concurrency warnings in Swift 6 I don't get any warnings. Just a runtime crash. How are we supposed to find these problems? Couldn't the compiler assist with a warning/error. Why does the compiler make the assumptions it does about the method that is declared like this: @available(iOS 9.0, *) open class func requestAutomaticPassPresentationSuppression(responseHandler: @escaping (PKAutomaticPassPresentationSuppressionResult) -> Void) -> PKSuppressionRequestToken Now that we have migrated to Swift 6 our code base contains a bunch of unknown places where it will crash as above.

I'm calling a method with the context as parameter, within the context's perform block – is this really not legal in Swift 6? actor MyActor { func bar(context: NSManagedObjectContext) { /* some code */ } func foo(context: NSManagedObjectContext) { context.performAndWait { self.bar(context: context) // WARN: Sending 'context' risks causing data races; this is an error in the Swift 6 language mode // 'self'-isolated 'context' is captured by a actor-isolated closure. actor-isolated uses in closure may race against later nonisolated uses // Access can happen concurrently } } } The warning appears when I call a method with a context parameter, within the performAndWait-block. Background: In my app I have methods that takes in API data, and I need to call the same methods from multiple places with the same context to store it, and I do not want to copy paste the code and have hundreds of lines of duplicate code. Is there a well-known "this is how you should do it" for situations like this? This is related to a previous post I made, but it's a bit flimsy and got no response: https://developer.apple.com/forums/thread/770605

I'm getting the following error in my SwiftUI code: "Main actor-isolated property 'avatarImage' can not be referenced from a Sendable closure" I don't understand how to fix it. This happens in the following code: You can copy-paste this into an empty project and make sure to have Swift 6 enabled under the Build Settings > Swift Language Version import PhotosUI import SwiftUI public struct ContentView: View { @State private var avatarItem: PhotosPickerItem? @State private var avatarImage: Image? @State private var avatarData: Data? public var body: some View { VStack(spacing: 30) { VStack(alignment: .center) { PhotosPicker(selection: $avatarItem, matching: .images) { if let avatarImage { avatarImage .resizable() .aspectRatio(contentMode: .fill) .frame(width: 100, height: 100) .foregroundColor(.gray) .background(.white) .clipShape(Circle()) .opacity(0.75) .overlay { Image(systemName: "pencil") .font(.title) .shadow(radius: 5) } } else { Image(systemName: "person.circle.fill") .resizable() .aspectRatio(contentMode: .fit) .frame(width: 100, height: 100) .foregroundColor(.gray) .background(.white) .clipShape(Circle()) .opacity(0.75) .overlay { Image(systemName: "pencil") .font(.title) .shadow(radius: 5) } } } } } .onChange(of: avatarItem) { Task { if let data = try? await avatarItem?.loadTransferable( type: Data.self ) { if let processed = processImage(data: data) { avatarImage = processed.image avatarData = processed.data } else { } } } } } private func processImage(data: Data) -> (image: Image?, data: Data?)? { guard let uiImage = UIImage(data: data)?.preparingForDisplay() else { return nil } // Check original size let sizeInMB = Double(data.count) / (1024 * 1024) // If image is larger than 1MB, compress it if sizeInMB > 1.0 { guard let compressedData = uiImage.compress() else { return nil } return (Image(uiImage: uiImage), compressedData) } return (Image(uiImage: uiImage), data) } } #Preview { ContentView() } public extension UIImage { func compress(to maxSizeInMB: Double = 1.0) -> Data? { let maxSizeInBytes = Int( maxSizeInMB * 1024 * 1024 ) // Convert MB to bytes var compression: CGFloat = 1.0 let step: CGFloat = 0.1 var imageData = jpegData(compressionQuality: compression) while (imageData?.count ?? 0) > maxSizeInBytes, compression > 0 { compression -= step imageData = jpegData(compressionQuality: compression) } return imageData } }

I am adopting Swift Concurrency in my network extension app to use Swift 6 protections. In the UI app I ended up with most of the app marked as MainActor, so that pieces of my app can keep seamless access to each other and at the same time have thread safe access. When it comes to my network extension, does it make sense to also mark most of the code as MainActor for the purposes of thread safety and seamless access of most classes to each other? I have doubts, because MainActor sounds like it should be a UI think, but network extension has no UI Of course any long or blocking operations would not be MainActor

Hi everyone, I believe this should be a simple and expected default behavior in a real-world app, but I’m unable to make it work: 1. I have a View (a screen/page in this case) that calls an endpoint using async/await. 2. If the endpoint hasn’t finished, but I navigate forward to a DetailView, I want the endpoint to continue fetching data (i.e., inside the @StateObject ViewModel that the View owns). This way, when I go back, the View will have refreshed with the fetched data once it completes. 3. If the endpoint hasn’t finished and I navigate back to the previous screen, I want it to be canceled, and the @StateObject ViewModel should be deinitialized. I can achieve 1 and 3 using the .task modifier, since it automatically cancels the asynchronous task when the view disappears: view .task { await vm.getData() } I can achieve 1 and 2 using a structured Task in the View (or in the ViewModel, its the same behavior), for example: .onFirstAppearOnly { Task { away vm.getData() } } onFirstAppearOnly is a custom modifier that I have for calling onAppear only once in view lifecycle. Just to clarify, dont think that part is important for the purpose of the example But the question is: How can I achieve all three behaviors? Is this really such an unusual requirement? My minimum deployment target is iOS 15, and I’m using NavigationView + NavigationLink. However, I have also tried using NavigationStack + NavigationPath and still couldn’t get it to work. Any help would be much appreciated. Thank you, folks!

Hi all, we try migrate project to Swift 6 Project use AVPlayer in MainActor Selection audio and subtitiles not work Task { @MainActor in let group = try await item.asset.loadMediaSelectionGroup(for: AVMediaCharacteristic.audible) get error: Non-sendable type 'AVMediaSelectionGroup?' returned by implicitly asynchronous call to nonisolated function cannot cross actor boundary and second example `if #available(iOS 15.0, *) { player?.currentItem?.asset.loadMediaSelectionGroup(for: AVMediaCharacteristic.audible, completionHandler: { group, error in if error != nil { return } if let groupWrp = group { DispatchQueue.main.async { self.setupAudio(groupWrp, audio: audioLang) } } }) }` get error: Sending 'groupWrp' risks causing data races

I've got a watch app, still with storyboard, WKInterfaceController and WatchConnectivity. After updating it for swift 6 concurrency I thought I'd keep it for a little while without swift 6 concurrency dynamic runtime check. So I added -disable-dynamic-actor-isolation in OTHER_SWIFT_FLAGS, but it doesn't seem to have an effect for the Apple Watch target. Without manually marking callbacks where needed with @Sendable in dynamic checks seem to be in place. swiftc invocation is as (includes -disable-dynamic-actor-isolation): swiftc -module-name GeoCameraWatchApp -Onone -enforce-exclusivity\=checked ... GeoCameraWatchApp.SwiftFileList -DDEBUG -enable-bridging-pch -disable-dynamic-actor-isolation -D DEBUG -enable-experimental-feature DebugDescriptionMacro -sdk /Applications/Xcode.app/Contents/Developer/Platforms/WatchOS.platform/Developer/SDKs/WatchOS11.2.sdk -target arm64_32-apple-watchos7.0 -g -module-cache-path /Users/stand/Library/Developer/Xcode/DerivedData/ModuleCache.noindex -Xfrontend -serialize-debugging-options -enable-testing -index-store-path /Users/stand/Library/Developer/Xcode/DerivedData/speedo-almhjmryctkitceaufvkvhkkfvdw/Index.noindex/DataStore -enable-experimental-feature OpaqueTypeErasure -Xcc -D_LIBCPP_HARDENING_MODE\=_LIBCPP_HARDENING_MODE_DEBUG -swift-version 6 ... -disable-dynamic-actor-isolation flag seems to be working for the iOS targets, I believe. The flag is described here Am I missing something? Should the flag work for both iOS and Apple Watch targets?

decidePolicyFor delegate method: import WebKit @objc extension DocumentationVC { func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction, decisionHandler: @escaping (WKNavigationActionPolicy) -> Void) Being called just alright in swift 5 minimal concurrency. Raising concurrency to complete with swift 5 or swift 6. Changing the code to avoid warnings: @preconcurrency import WebKit @objc extension DocumentationVC { func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction, decisionHandler: @escaping (WKNavigationActionPolicy) -> Void) { The delegate method is not being called. Changing back to swift 5 concurrency minimal - it is called. Looking at WKNavigationDelegate: WK_SWIFT_UI_ACTOR @protocol WKNavigationDelegate <NSObject> - (void)webView:(WKWebView *)webView decidePolicyForNavigationAction:(WKNavigationAction *)navigationAction decisionHandler:(WK_SWIFT_UI_ACTOR void (^)(WKNavigationActionPolicy))decisionHandler WK_SWIFT_ASYNC(3); Changing the delegate method to: func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction, decisionHandler: @escaping @MainActor (WKNavigationActionPolicy) -> Void) { And it is called across swift 5 concurrency minimal to complete to swift 6. I thought, the meaning of @preconcurrency import WebKit was to keep the delegate without @MainActor before the (WKNavigationActionPolicy) still matching regardless the swift concurrency mode? My point is - this can introduce hidden breaking changes? I didn't see this documented anyhow at: https://www.swift.org/migration/documentation/migrationguide/. decidePolicyFor is an optional method - so if signature 'mismatches' - there will be no warning on not-implementing the delegate method. How do we catch or diagnose irregularities like this? Is it something @preconcurrency import WebKit should be ensuring and it is not? Is this delegate mismatch a bug on swift side or something we should be taking care of while migrating? If it is on us, how do we diagnose these potential mismatches?

Hey all! During the migration of a production app to swift 6, I've encountered a problem: when hitting the UNUserNotificationCenter.current().requestAuthorization the app crashes. If I switch back to Language Version 5 the app works as expected. The offending code is defined here class AppDelegate: NSObject, UIApplicationDelegate { func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -&gt; Bool { FirebaseApp.configure() FirebaseConfiguration.shared.setLoggerLevel(.min) UNUserNotificationCenter.current().delegate = self let authOptions: UNAuthorizationOptions = [.alert, .badge, .sound] UNUserNotificationCenter.current().requestAuthorization(options: authOptions) { _, _ in } application.registerForRemoteNotifications() Messaging.messaging().delegate = self return true } } The error is depicted here: I have no idea how to fix this. Any help will be really appreciated thanks in advance

Hello. I am building an app that shows my walk workouts and in the detail view I want to show the route I took while walking, similar to that of the Apple Fitness App. There is a problem though, I cannot seem to understand how to connect the @State property workoutLocations array that would be used to draw the route on the map with what I get from the query. The task does successfully fetches the data but then when I try to use it later in a do-catch block nothing happens. What am I missing here? import SwiftUI import MapKit import HealthKit struct DetailView: View { @Environment(HealthKitManager.self) var healthKitManager let workout: HKWorkout @State private var workoutLocations: [CLLocation] = [] var body: some View { ScrollView { //... } .task { guard let store = self.healthKitManager.healthStore else { fatalError("healthStore is nil. App is in invalid state.") } let walkingObjectQuery = HKQuery.predicateForObjects(from: workout) let routeQuery = HKAnchoredObjectQueryDescriptor(predicates: [.workoutRoute(walkingObjectQuery)], anchor: nil) let queryResults = routeQuery.results(for: store) let task = Task { var workoutRouteLocations: [CLLocation] = [] for try await result in queryResults { let routeSamples = result.addedSamples for routeSample in routeSamples { let routeQueryDescriptor = HKWorkoutRouteQueryDescriptor(routeSample) let locations = routeQueryDescriptor.results(for: store) for try await location in locations { workoutRouteLocations.append(location) print(workoutRouteLocations.count) // this prints out the number of locations in the sample. } } } return workoutRouteLocations } do { print(try await task.value.count) // this prints nothing. Therefore if I try to update workoutLocations array from here it would do nothing as well // workoutLocations = try await task.value therefore does nothing and the array just doesn't get populated with the results of the task } catch { print(error) } } } }

Based on crash reports for our app in production, we're seeing these SwiftUI crashes but couldn't figure out why it is there. These crashes are pretty frequent (>20 crashed per day). Would really appreciate it if anyone has any insight on why this happens. Based on the stacktrace, i can't really find anything that links back to our app (replaced with MyApp in the stacktrace). Thank you in advance! Crashed: com.apple.main-thread 0 libdispatch.dylib 0x39dcc _dispatch_semaphore_dispose.cold.1 + 40 1 libdispatch.dylib 0x4c1c _dispatch_semaphore_signal_slow + 82 2 libdispatch.dylib 0x2d30 _dispatch_dispose + 208 3 SwiftUICore 0x77f788 destroy for StoredLocationBase.Data + 64 4 libswiftCore.dylib 0x3b56fc swift_arrayDestroy + 196 5 libswiftCore.dylib 0x13a60 UnsafeMutablePointer.deinitialize(count:) + 40 6 SwiftUICore 0x95f374 AtomicBuffer.deinit + 124 7 SwiftUICore 0x95f39c AtomicBuffer.__deallocating_deinit + 16 8 libswiftCore.dylib 0x3d783c _swift_release_dealloc + 56 9 libswiftCore.dylib 0x3d8950 bool swift::RefCounts<swift::RefCountBitsT<(swift::RefCountInlinedness)1>>::doDecrementSlow<(swift::PerformDeinit)1>(swift::RefCountBitsT<(swift::RefCountInlinedness)1>, unsigned int) + 160 10 SwiftUICore 0x77e53c StoredLocation.deinit + 32 11 SwiftUICore 0x77e564 StoredLocation.__deallocating_deinit + 16 12 libswiftCore.dylib 0x3d783c _swift_release_dealloc + 56 13 libswiftCore.dylib 0x3d8950 bool swift::RefCounts<swift::RefCountBitsT<(swift::RefCountInlinedness)1>>::doDecrementSlow<(swift::PerformDeinit)1>(swift::RefCountBitsT<(swift::RefCountInlinedness)1>, unsigned int) + 160 14 MyApp 0x1673338 objectdestroyTm + 6922196 15 libswiftCore.dylib 0x3d783c _swift_release_dealloc + 56 16 libswiftCore.dylib 0x3d8950 bool swift::RefCounts<swift::RefCountBitsT<(swift::RefCountInlinedness)1>>::doDecrementSlow<(swift::PerformDeinit)1>(swift::RefCountBitsT<(swift::RefCountInlinedness)1>, unsigned int) + 160 17 SwiftUICore 0x650290 _AppearanceActionModifier.MergedBox.__deallocating_deinit + 32 18 libswiftCore.dylib 0x3d783c _swift_release_dealloc + 56 19 libswiftCore.dylib 0x3d8950 bool swift::RefCounts<swift::RefCountBitsT<(swift::RefCountInlinedness)1>>::doDecrementSlow<(swift::PerformDeinit)1>(swift::RefCountBitsT<(swift::RefCountInlinedness)1>, unsigned int) + 160 20 SwiftUICore 0x651b44 closure #1 in _AppearanceActionModifier.MergedBox.update()partial apply + 28 21 libswiftCore.dylib 0x3d783c _swift_release_dealloc + 56 22 libswiftCore.dylib 0x3d8950 bool swift::RefCounts<swift::RefCountBitsT<(swift::RefCountInlinedness)1>>::doDecrementSlow<(swift::PerformDeinit)1>(swift::RefCountBitsT<(swift::RefCountInlinedness)1>, unsigned int) + 160 23 libswiftCore.dylib 0x3b56fc swift_arrayDestroy + 196 24 libswiftCore.dylib 0xa2a54 _ContiguousArrayStorage.__deallocating_deinit + 96 25 libswiftCore.dylib 0x3d783c _swift_release_dealloc + 56 26 libswiftCore.dylib 0x3d8950 bool swift::RefCounts<swift::RefCountBitsT<(swift::RefCountInlinedness)1>>::doDecrementSlow<(swift::PerformDeinit)1>(swift::RefCountBitsT<(swift::RefCountInlinedness)1>, unsigned int) + 160 27 SwiftUICore 0x4a6c4c type metadata accessor for _ContiguousArrayStorage<CVarArg> + 120 28 libswiftCore.dylib 0x3d783c _swift_release_dealloc + 56 29 libswiftCore.dylib 0x3d8950 bool swift::RefCounts<swift::RefCountBitsT<(swift::RefCountInlinedness)1>>::doDecrementSlow<(swift::PerformDeinit)1>(swift::RefCountBitsT<(swift::RefCountInlinedness)1>, unsigned int) + 160 30 SwiftUICore 0x4a5d88 static Update.dispatchActions() + 1332 31 SwiftUICore 0xa0db28 closure #2 in closure #1 in ViewRendererHost.render(interval:updateDisplayList:targetTimestamp:) + 132 32 SwiftUICore 0xa0d928 closure #1 in ViewRendererHost.render(interval:updateDisplayList:targetTimestamp:) + 708 33 SwiftUICore 0xa0b0d4 ViewRendererHost.render(interval:updateDisplayList:targetTimestamp:) + 556 34 SwiftUI 0x8f1634 UIHostingViewBase.renderForPreferences(updateDisplayList:) + 168 35 SwiftUI 0x8f495c closure #1 in UIHostingViewBase.requestImmediateUpdate() + 72 36 SwiftUI 0xcc700 thunk for @escaping @callee_guaranteed () -> () + 36 37 libdispatch.dylib 0x2370 _dispatch_call_block_and_release + 32 38 libdispatch.dylib 0x40d0 _dispatch_client_callout + 20 39 libdispatch.dylib 0x129e0 _dispatch_main_queue_drain + 980 40 libdispatch.dylib 0x125fc _dispatch_main_queue_callback_4CF + 44 41 CoreFoundation 0x56204 __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 16 42 CoreFoundation 0x53440 __CFRunLoopRun + 1996 43 CoreFoundation 0x52830 CFRunLoopRunSpecific + 588 44 GraphicsServices 0x11c4 GSEventRunModal + 164 45 UIKitCore 0x3d2eb0 -[UIApplication _run] + 816 46 UIKitCore 0x4815b4 UIApplicationMain + 340 47 SwiftUI 0x101f98 closure #1 in KitRendererCommon(_:) + 168 48 SwiftUI 0xe2664 runApp<A>(_:) + 100 49 SwiftUI 0xe5490 static App.main() + 180 50 MyApp 0x8a7828 main + 4340250664 (MyApp.swift:4340250664) 51 ??? 0x1ba496ec8 (Missing)

Based on the iPhone 14 Max camera, implement model recognition and draw a rectangular box around the recognized object. The width and height are calculated using LiDAR and displayed in centimeters on the real-time updated image.

I'm trying to fix some Swift6 warnings, this one seems too strict, I'm not sure how to fix it. The variable path is a String, which should be immutable, it's a local variable and never used again inside of the function, but still Swift6 complains about it being a race condition, passing it to the task What should I do here to fix the warning?

Hello there, I need to move through video loaded in an AVPlayer one frame at a time back or forth. For that I tried to use AVPlayerItem's method step(byCount:) and it works just fine. However I need to know when stepping happened and as far as I observed it is not immediate using the method. If I check the currentTime() just after calling the method it's the same and if I do it slightly later (depending of the video itself) it shows the correct "jumped" time. To achieve my goal I tried subclassing AVPlayerItem and implement my own async method utilizing NotificationCenter and the timeJumpedNotification assuming it would deliver it as the time actually jumps but it's not the case. Here is my "stripped" and simplified version of the custom Player Item: import AVFoundation final class PlayerItem: AVPlayerItem { private var jumpCompletion: ( (CMTime) -> () )? override init(asset: AVAsset, automaticallyLoadedAssetKeys: [String]?) { super .init(asset: asset, automaticallyLoadedAssetKeys: automaticallyLoadedAssetKeys) NotificationCenter.default.addObserver(self, selector: #selector(timeDidChange(_:)), name: AVPlayerItem.timeJumpedNotification, object: self) } deinit { NotificationCenter.default.removeObserver(self, name: AVPlayerItem.timeJumpedNotification, object: self) jumpCompletion = nil } @discardableResult func step(by count: Int) async -> CMTime { await withCheckedContinuation { continuation in step(by: count) { time in continuation.resume(returning: time) } } } func step(by count: Int, completion: @escaping ( (CMTime) -> () )) { guard jumpCompletion == nil else { completion(currentTime()) return } jumpCompletion = completion step(byCount: count) } @objc private func timeDidChange(_ notification: Notification) { switch notification.name { case AVPlayerItem.timeJumpedNotification where notification.object as? AVPlayerItem [==](https://www.example.com/) self: jumpCompletion?(currentTime()) jumpCompletion = nil default: return } } } In short the notification never gets called thus the above is not working. I guess the key there is that in the docs about the timeJumpedNotification: is said: "A notification the system posts when a player item’s time changes discontinuously." so the step(byCount:) is not considered as discontinuous operation and doesn't trigger it. I'd be really helpful if somebody can help as I don't want to use seek(to:toleranceBefore:toleranceAfter:) mainly cause it's not accurate in terms of the exact next/previous frame as the video might have VFR and that causes repeating frames sometimes or even skipping one or another. Thanks a lot

I’m currently developing an iOS metronome app using DispatchSourceTimer as the timer. The interval is set very small, around 50 milliseconds, and I’m using CFAbsoluteTimeGetCurrent to calculate the elapsed time to ensure the beat is played within a ±0.003-second margin. The problem is that once the app goes to the background, the timing becomes unstable—it slows down noticeably, then recovers after 1–2 seconds. When coming back to the foreground, it suddenly speeds up, and again, it takes 1–2 seconds to return to normal. It feels like the app is randomly “powering off” and then “overclocking.” It’s super frustrating. I’ve noticed that some metronome apps in the App Store have similar issues, but there’s one called “Professional Metronome” that’s rock solid with no such problems. What kind of magic are they using? Any experts out there who can help? Thanks in advance! P.S. I’ve already enabled background audio permissions. The professional metronome that has no issues: https://link.zhihu.com/?target=https%3A//apps.apple.com/cn/app/pro-metronome-%25E4%25B8%2593%25E4%25B8%259A%25E8%258A%2582%25E6%258B%258D%25E5%2599%25A8/id477960671

When using the continuation API, we're required to call resume exactly once. While withCheckedContinuation helps catch runtime issues during debugging, I'm looking for ways to catch such errors at compile time or through tools like Instruments. Is there any tool or technique that can help enforce or detect this requirement more strictly than runtime checks? Or would creating custom abstractions around Continuation be the only option to ensure safety? Any suggestions or best practices are appreciated.