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Programming Languages Resources
This topic area is about the programming languages themselves, not about any specific API or tool. If you have an API question, go to the top level and look for a subtopic for that API. If you have a question about Apple developer tools, start in the Developer Tools & Services topic. For Swift questions: If your question is about the SwiftUI framework, start in UI Frameworks > SwiftUI. If your question is specific to the Swift Playground app, ask over in Developer Tools & Services > Swift Playground If you’re interested in the Swift open source effort — that includes the evolution of the language, the open source tools and libraries, and Swift on non-Apple platforms — check out Swift Forums If your question is about the Swift language, that’s on topic for Programming Languages > Swift, but you might have more luck asking it in Swift Forums > Using Swift. General: Forums topic: Programming Languages Swift: Forums subtopic: Programming Languages > Swift Forums tags: Swift Developer > Swift website Swift Programming Language website The Swift Programming Language documentation Swift Forums website, and specifically Swift Forums > Using Swift Swift Package Index website Concurrency Resources, which covers Swift concurrency How to think properly about binding memory Swift Forums thread Other: Forums subtopic: Programming Languages > Generic Forums tags: Objective-C Programming with Objective-C archived documentation Objective-C Runtime documentation Share and Enjoy — Quinn “The Eskimo!” @ Developer Technical Support @ Apple let myEmail = "eskimo" + "1" + "@" + "apple.com"
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Oct ’25
What is the future of Objective-C?
Will Apple continue to support it, or will we wake up one day to find that Swift is the only viable language?It's a serious question. Careers depend on it. I don't accept the "No comment" approach that Apple usually takes. It's cruel.I'm willing to put the time into learning Swift if I have to. I'm not going to do it if I don't. I want to know.Frank
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34k
Oct ’25
Open Share Extension
Hello, everyone! Help me please to find answer. I have two applications: App-1 with share extension and App-2 without it. From the second app I can open share extension via UIActivityViewController. But I need this extension in the second application to open immediately by pressing a button, and not through UIActivityViewController. Can I do this?
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1.6k
Dec ’24
Crash with Progress type, Swift 6, iOS 18
We are getting a crash _dispatch_assert_queue_fail when the cancellationHandler on NSProgress is called. We do not see this with iOS 17.x, only on iOS 18. We are building in Swift 6 language mode and do not have any compiler warnings. We have a type whose init looks something like this: init( request: URLRequest, destinationURL: URL, session: URLSession ) { progress = Progress() progress.kind = .file progress.fileOperationKind = .downloading progress.fileURL = destinationURL progress.pausingHandler = { [weak self] in self?.setIsPaused(true) } progress.resumingHandler = { [weak self] in self?.setIsPaused(false) } progress.cancellationHandler = { [weak self] in self?.cancel() } When the progress is cancelled, and the cancellation handler is invoked. We get the crash. The crash is not reproducible 100% of the time, but it happens significantly often. Especially after cleaning and rebuilding and running our tests. * thread #4, queue = 'com.apple.root.default-qos', stop reason = EXC_BREAKPOINT (code=1, subcode=0x18017b0e8) * frame #0: 0x000000018017b0e8 libdispatch.dylib`_dispatch_assert_queue_fail + 116 frame #1: 0x000000018017b074 libdispatch.dylib`dispatch_assert_queue + 188 frame #2: 0x00000002444c63e0 libswift_Concurrency.dylib`swift_task_isCurrentExecutorImpl(swift::SerialExecutorRef) + 284 frame #3: 0x000000010b80bd84 MyTests`closure #3 in MyController.init() at MyController.swift:0 frame #4: 0x000000010b80bb04 MyTests`thunk for @escaping @callee_guaranteed @Sendable () -> () at <compiler-generated>:0 frame #5: 0x00000001810276b0 Foundation`__20-[NSProgress cancel]_block_invoke_3 + 28 frame #6: 0x00000001801774ec libdispatch.dylib`_dispatch_call_block_and_release + 24 frame #7: 0x0000000180178de0 libdispatch.dylib`_dispatch_client_callout + 16 frame #8: 0x000000018018b7dc libdispatch.dylib`_dispatch_root_queue_drain + 1072 frame #9: 0x000000018018bf60 libdispatch.dylib`_dispatch_worker_thread2 + 232 frame #10: 0x00000001012a77d8 libsystem_pthread.dylib`_pthread_wqthread + 224 Any thoughts on why this is crashing and what we can do to work-around it? I have not been able to extract our code into a simple reproducible case yet. And I mostly see it when running our code in a testing environment (XCTest). Although I have been able to reproduce it running an app a few times, it's just less common.
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2.7k
Apr ’25
MPMediaItemPropertyArtwork crashes on Swift 6
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
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3.0k
Sep ’25
Actors with Combine publishers as properties.
Is it ok for an Actor type to have a Publisher as a property to let others observe changes over time? Or use the @Published property wrapper to achieve this? actor MyActor { var publisher = PassthroughSubject<Int, Never>() var data: Int { didSet { publisher.send(data) } } ... } // Usage var tasks = Set<AnyCancellable>() let actor = MyActor() Task { let publisher = await actor.publisher publisher.sink { print($0) }.store(in: &tasks) } This seems like this should be acceptable. I would expect a Publisher to be thread safe, and as long as the Output is a value type things should be fine. I have been getting random EXC_BAD_ACCESS errors when using this approach. But turning on the address sanitizer causes these crashes to go away. I know that isn't very specific but I wanted to start by seeing if this type of pattern is ok to do.
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2.6k
Apr ’25
[WindowHosting] UIScene property of UINSSceneViewController was accessed before it was set. What does this mean?
Getting this error several times when presenting a modal window over my splitview window when running it on my Mac using Swift/Mac Catalyst in XCode 14.2. When I click the Cancel button in the window then I get Scene destruction request failed with error: (null) right after an unwind segue. 2023-07-04 16:50:45.488538-0500 Recipes[27836:1295134] [WindowHosting] UIScene property of UINSSceneViewController was accessed before it was set. 2023-07-04 16:50:45.488972-0500 Recipes[27836:1295134] [WindowHosting] UIScene property of UINSSceneViewController was accessed before it was set. 2023-07-04 16:50:45.496702-0500 Recipes[27836:1295134] [WindowHosting] UIScene property of UINSSceneViewController was accessed before it was set. 2023-07-04 16:50:45.496800-0500 Recipes[27836:1295134] [WindowHosting] UIScene property of UINSSceneViewController was accessed before it was set. 2023-07-04 16:50:45.994147-0500 Recipes[27836:1295134] Unbalanced calls to begin/end appearance transitions for <UINavigationController: 0x7f7fdf068a00>. bleep 2023-07-04 16:51:00.655233-0500 Recipes[27836:1297298] Scene destruction request failed with error: (null) I don't quite understand what all all this means. (The "bleep" was a debugging print code I put in the unwind segue). I'm working through Apple's Mac Catalyst tutorial but it seems to be riddled with bugs and coding issues, even in the final part of the completed app which I dowmloaded and ran. I don't see these problems on IPad simulator. I don't know if it's because Catalyst has problems itself or there's something else going on that I can fix myself. Any insight into these errors would be very much appreciated! PS: The app seems to run ok on Mac without crashing despite the muliple issues
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2k
Jan ’25
Error throws while using the speech recognition service in my app
Recently I updated to Xcode 14.0. I am building an iOS app to convert recorded audio into text. I got an exception while testing the application from the simulator(iOS 16.0). [SpeechFramework] -[SFSpeechRecognitionTask handleSpeechRecognitionDidFailWithError:]_block_invoke Ignoring subsequent recongition error: Error Domain=kAFAssistantErrorDomain Code=1101 "(null)" Error Domain=kAFAssistantErrorDomain Code=1107 "(null)" I have to know what does the error code means and why this error occurred.
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12k
Feb ’25
Request authorization for the notification center crash iOS app on Swift 6
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
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5.6k
Jan ’25
.onMove does not work properly
Hello, I have a problem with the .onMove function. I believe I have set everything up properly. However, the moving does not seem to be working correctly. When I try to move the item, it is highlighted first, as it is supposed to be. Then, while I am moving it through the list, it disappears for some reason, and at the end of the move, it comes back to its initial place. (I use iOS 16.0 minimum, so I don't have to include the EditButton(). It works the same in the edit mode tho) import SwiftUI struct Animal: Identifiable { var id = UUID() var name: String } struct ListMove: View { @State var animals = [Animal(name: "Dog"), Animal(name: "Cat"), Animal(name: "Cow"), Animal(name: "Goat"), Animal(name: "Chicken")] var body: some View { List { ForEach(animals) { animal in Text(animal.name) } .onMove(perform: move) } } func move(from source: IndexSet, to destination: Int) { animals.move(fromOffsets: source, toOffset: destination) } } #Preview { ListMove() }
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1.2k
Dec ’24
NotificationCenter Crash On iOS 18+ Swift6.2
After switching our iOS app project from Swift 5 to Swift 6 and publishing an update, we started seeing a large number of crashes in Firebase Crashlytics. The crashes are triggered by NotificationCenter methods (post, addObserver, removeObserver) and show the following error: BUG IN CLIENT OF LIBDISPATCH: Assertion failed: Block was expected to execute on queue [com.apple.main-thread (0x1f9dc1580)] All scopes to related calls are already explicitly marked with @MainActor. This issue never occurred with Swift 5, but appeared immediately after moving to Swift 6. Has anyone else encountered this problem? Is there a known solution or workaround? Thanks in advance!
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1.4k
2w
Why does Array.contains cause a compile-time error when comparing an optional value with a non-optional value in Swift?
I’m working with Swift and ran into an issue when using the contains(_:) method on an array. The following code works fine: let result = ["hello", "world"].contains(Optional("hello")) // ✅ Works fine But when I try to use the same contains method with the array declared in a separate variable, I get a compile-time error: let stringArray = ["hello", "world"] let result = stringArray.contains(Optional("hello")) // ❌ Compile-time error Both examples seem conceptually similar, but the second one causes a compile-time error, while the first one works fine. I understand that when comparing an optional value (Optional("hello")) with a non-optional value ("hello"), Swift automatically promotes the non-optional value to an optional (i.e., "hello" becomes Optional("hello")). 🔗 reference What I don’t understand is why the first code works but the second one doesn’t, even though both cases involve comparing an optional value with a non-optional value. I know that there are different ways to resolve this, like using nil coalescing or optional binding, but what I’m really looking for is a detailed explanation of why this issue occurs at the compile-time level. Can anyone explain the underlying reason for this behavior?
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Mar ’25
Update or remove Ruby 2.6
macOS Tahoe ships with Ruby 2.6.10 which was End Of Life in April 2022 (https://www.ruby-lang.org/en/downloads/branches/). How can I either upgrade it to Ruby 3.4.7 or delete it, so that my mac meets minimum cybersecurity requirements? I use rbenv for more recent versions of Ruby at the moment so don't need any suggestions on how to do add them, I just need rid of the dangerously out of date system Ruby, thanks.
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1w
Open any Swift view from C++
I've narrowed down my question after many rabbit holes - how can C++ code open any view in Swift. I can call functions in swift from C++ (works great), but not async or main actor (or actor at all) functions. And if I'm not mistaken all views are actors if not main actors? When calling from C+ I think its necessary that the first view be the main actor? I've implemented the code from the WWDC23 C++ interop video (Zoe's image picker) where I made a view in a struct, and just want to call it and let the view do the work. The compiler immediately gives me 'cannot expose main actors to C++'. If I'm not mistaken, doesn't this block the opening of any kind of swift view from C++? Hopefully I'm missing something obvious, which is likely :) In Zoe's code was his entry point into the program still Swift and not actually C++ app? Thanks! Thanks!
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May ’25
Unexpected behavior of dispatch_main on macOS
Hi! We are seeing a bit surprising behavior of dispatch_main on macOS where it seems to spawn a different thread instead of preserving the one it gets called from. Managed to reproduce it in a completely empty command-line tool project in Xcode int main(int argc, const char * argv[]) { @autoreleasepool { dispatch_main(); return 0; } } I put a breakpoint on the line with dispatch_main and see that I am on Thread 1 and inside main function. That makes sense. I resume execution and pause again. Looking at Thread output in Xcode, I can only see Thread 2. Thread 1 is gone and the executable keeps on running. So dispatch_main did what was expected (prevented the process from termination) but throws out the thread it was called from and creates a new one? Is that behavior expected or am I missing something? Just a brain teaser at this point. But we could not make sense out of it. :)
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569
Jan ’25
indices(where:) Swift Playgrounds Issue: "Cannot call value of non-function type Range<Int>"
Hey there- I'm having a quite interesting bug on Swift Playgrounds. I am trying to run my app with this following code snippet which does not compile on Swift Playgrounds, yet compiles on XCode (note: this is a Swift Playground app) if #available(iOS 18.0, *) { //simple function to get the indices of other items that have the same date as the "date" variable let indices = data!.indices(where: { item in let sameMonth = Calendar.current.component(.month, from: item.time) == Calendar.current.component(.month, from: date) let sameYear = Calendar.current.component(.year, from: item.time) == Calendar.current.component(.year, from: date) let sameDay = Calendar.current.component(.day, from: item.time) == Calendar.current.component(.year, from: date) return sameDay && sameMonth && sameYear }) However, the indices(where:) codeblock seems to stop the app from compiling (ONLY on Swift Playgrounds - it works perfectly fine on XCode). I am getting the following error: Cannot call value of non-function type 'Range<Array<Int>.Index>' (aka 'Range<Int>') Please let me know if you have any insight regarding this issue. -ColoredOwl
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567
Jan ’25
New unexpected compile behavior in Xcode 16.3
I have a macro that converts expression into a string literal, e.g.: #toString(variable) -> "variable" #toString(TypeName) -> "TypeName" #toString(\TypeName.property) -> "property" In Xcode 16.3 #toString(TypeName) stopped to work, compilation throws 'Expected member name or initializer call after type name' error. Everything works fine in Xcode 16.2. I tried to compare build settings between 16.2 and 16.3 but haven't noticed differences that may cause this new error. The following works in both Xcode versions: #toString(variable) -> "variable" #toString(\TypeName.property) -> "property" Seems like Xcode tries to compile code that shouldn't be compiled because of macro expansion. Does anybody know what new has appeared in 16.3 and, perhaps, how to fix the problem?
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Apr ’25