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Using Observations with SwiftData @Model
I want to use the Observations AsyncSequence on some SwiftData @Model instances to determine if internal calculations need to be done. When a simple property is linked to the Observations it fires CONTINUOUSLY even though no change is made to the model property. Also, when I try to observe a property which is a list of another @Model type the Observations sequence does not fire when I add or remove items. I am hoping to use the async-algorithm's merge function so all the associated sequences can be combined since if any of the associated events should fire the calculation event.
4
0
2.8k
Jan ’26
JavaScript/Swift Interoperability
I think that it would be helpful to have better interoperability between Swift and JavaScript. There are a lot of useful packages on NPM that don't have equivalents for Swift. It would be helpful if Apple provided easier ways to use NPM packages in a Swift project. Currently, the JavaScriptCore framework is missing many standard things used in many packages, like the fetch API. It would be helpful to be able to run sandboxed JavaScript code inside of a Swift app but allow access to specific domains, folders, etc., using a permissions system similar to Deno.
6
1
3.3k
Jan ’26
Calling a Objc method directly from C
I would like to avoid the middle man and call Objective C directly from C Currently I do this This is called from a dispatch table in a pure C file _ctx->mt_render_funcs.mtlEnd(_ctx); Which calls this routine in a obj c file .m void mtlEnd(MTRenderContext mt_ctx) { // Call the Objective-C method using Objective-C syntax [(__bridge id) mt_ctx->mt_render_funcs.mtlObj mtlEnd]; } Which ends up here... in ObjC #pragma mark mtlEnd (void)mtlEnd { // vertex buffer size_t size; size = sizeof(Vertex4ColorNormalTex) * _ctx->vert_eng.current_vertex; [_currentRenderEncoder setVertexBytes:_ctx->vert_eng.vertices length: size atIndex: VertexInputIndexVertices]; [_currentRenderEncoder drawPrimitives:(MTLPrimitiveType)_ctx->vert_eng.prim_type vertexStart:0 vertexCount:_ctx->vert_eng.current_vertex]; } It would simplify this to get rid of one call and call ObjC directly. The other idea is I want to use GCD and put a lock / unlock on the call from C to ensure thread safety so I can use GCD to dispatch a thread to do the ObjC routines. I want to stick with C as the foundation so it can be used directly from C or a FFI interface from other languages. But Metal works well in ObjC and I would prefer to use that. Thanks ahead of time.
3
0
1.2k
Mar ’26
Why is the Documentation full of Conundrums?
I'm trying to learn and focus on the task and your examples keep having hidden conundrums in them. Here is an example that got me snagged for hours last night going, Well what the F do they want me to name it? What is it you want me to learn here? Because you pose a giant riddle of name something that you should be given a name for... My friend said to me that this is a common thing you will have to do and they were right however... What are you asking me to do? Get stuck on the variable naming problem where I'm going... Yeah those are math terms from 20+ years ago and I have no idea how to classify those terms... Are you asking me that? No. So why is that in the problem. These conundrums mixed in with legitimate problems honestly make me not want to learn Swift at all.
3
0
291
2w
On iPad with Swift Playgrounds: How to open chapter as a playground?
Note On a Mac with Xcode installed, or on an iPad with Swift Playgrounds, you can open this chapter as a playground. Playgrounds allow you to edit the code listings and see the results immediately. (Note in page 3) (I would like to open the chapter or book: Swift Programming Language in Swift Playground on iPad) https://books.apple.com/ve/book/the-swift-programming-language-swift-5-7-beta/id1002622538?l=en-GB Best regards
1
0
753
2w
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!
2
1
1.6k
Nov ’25
iOS and Android
I currently have a iOS app live on the App Store but I also want to release it on Android, the whole code is in Swift so would that be possible or would I have to rewrite my whole apps code in a different coding language.
2
0
2.7k
Jan ’26
Data Disappeared
Hi, writing a database app for storing equipment details. Spent the day doing minor changes and tidying with many backups made, and always re-building to check its all working. Everything ok but then next build looses all data, what's the best thing to check to see if the data is still there, any help would be fantastic.
1
0
1.2k
3w
Apple Silicon calling printf
What is the proper way to pass arguments to printf with multiple variables using ARM64 Apple Silicon? Example: fOutputStr: .asciz "Element[%d] = %d\n" // formated output string for an output of: Element[4] = 9 This code (see below) works on Raspberry Pi 5, on my Mac Studio, I am getting this output, Element[9] = 1871655168 What do I need to do to use printf from an assembly language call with multiple variables? I am using the following code. ` .align 2 // memory alignment model for 64-bit ARMc #if defined(APPLE) .global _main // Provide program starting address to linker Mac OS _main: #else .global main // Raspian and Linux main: #endif // stack frame work setup START stp x29, x30, [sp, -16]! str x20, [sp, -16]! mov x29, sp // stack frame work setup END // setup printf call #if defined(APPLE) adrp x0, fOutputStr@PAGE add x0, x0, fOutputStr@PAGEOFF #else ldr x0, =fOutputStr #endif mov w1, #4 mov w2, #9 print_brk: #if defined(APPLE) stp X0, X1, [SP, #-16]! stp X2, X3, [SP, #-16]! bl _printf ldp X2, X3, [SP], #16 ldp X0, X1, [SP], #16 #else bl printf #endif done: // closing stack frame work ldr x20, [sp],16 ldp x29, x30, [sp],16 // exit mov w0, wzr ret .data .align 4 // intArrayPtr: .word 3,7,5,2,4,8 // word, each value is offset by 4 fOutputStr: .asciz "Element[%d] = %d\n" // formated output string
6
1
743
2w
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.
1
6
2.8k
Apr ’25
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 () -&gt; () at &lt;compiler-generated&gt;: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.
24
7
3.1k
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
6
0
3.1k
Sep ’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
23
1
34k
Oct ’25
Using Observations with SwiftData @Model
I want to use the Observations AsyncSequence on some SwiftData @Model instances to determine if internal calculations need to be done. When a simple property is linked to the Observations it fires CONTINUOUSLY even though no change is made to the model property. Also, when I try to observe a property which is a list of another @Model type the Observations sequence does not fire when I add or remove items. I am hoping to use the async-algorithm's merge function so all the associated sequences can be combined since if any of the associated events should fire the calculation event.
Replies
4
Boosts
0
Views
2.8k
Activity
Jan ’26
JavaScript/Swift Interoperability
I think that it would be helpful to have better interoperability between Swift and JavaScript. There are a lot of useful packages on NPM that don't have equivalents for Swift. It would be helpful if Apple provided easier ways to use NPM packages in a Swift project. Currently, the JavaScriptCore framework is missing many standard things used in many packages, like the fetch API. It would be helpful to be able to run sandboxed JavaScript code inside of a Swift app but allow access to specific domains, folders, etc., using a permissions system similar to Deno.
Replies
6
Boosts
1
Views
3.3k
Activity
Jan ’26
Calling a Objc method directly from C
I would like to avoid the middle man and call Objective C directly from C Currently I do this This is called from a dispatch table in a pure C file _ctx->mt_render_funcs.mtlEnd(_ctx); Which calls this routine in a obj c file .m void mtlEnd(MTRenderContext mt_ctx) { // Call the Objective-C method using Objective-C syntax [(__bridge id) mt_ctx->mt_render_funcs.mtlObj mtlEnd]; } Which ends up here... in ObjC #pragma mark mtlEnd (void)mtlEnd { // vertex buffer size_t size; size = sizeof(Vertex4ColorNormalTex) * _ctx->vert_eng.current_vertex; [_currentRenderEncoder setVertexBytes:_ctx->vert_eng.vertices length: size atIndex: VertexInputIndexVertices]; [_currentRenderEncoder drawPrimitives:(MTLPrimitiveType)_ctx->vert_eng.prim_type vertexStart:0 vertexCount:_ctx->vert_eng.current_vertex]; } It would simplify this to get rid of one call and call ObjC directly. The other idea is I want to use GCD and put a lock / unlock on the call from C to ensure thread safety so I can use GCD to dispatch a thread to do the ObjC routines. I want to stick with C as the foundation so it can be used directly from C or a FFI interface from other languages. But Metal works well in ObjC and I would prefer to use that. Thanks ahead of time.
Replies
3
Boosts
0
Views
1.2k
Activity
Mar ’26
Why is the Documentation full of Conundrums?
I'm trying to learn and focus on the task and your examples keep having hidden conundrums in them. Here is an example that got me snagged for hours last night going, Well what the F do they want me to name it? What is it you want me to learn here? Because you pose a giant riddle of name something that you should be given a name for... My friend said to me that this is a common thing you will have to do and they were right however... What are you asking me to do? Get stuck on the variable naming problem where I'm going... Yeah those are math terms from 20+ years ago and I have no idea how to classify those terms... Are you asking me that? No. So why is that in the problem. These conundrums mixed in with legitimate problems honestly make me not want to learn Swift at all.
Replies
3
Boosts
0
Views
291
Activity
2w
On iPad with Swift Playgrounds: How to open chapter as a playground?
Note On a Mac with Xcode installed, or on an iPad with Swift Playgrounds, you can open this chapter as a playground. Playgrounds allow you to edit the code listings and see the results immediately. (Note in page 3) (I would like to open the chapter or book: Swift Programming Language in Swift Playground on iPad) https://books.apple.com/ve/book/the-swift-programming-language-swift-5-7-beta/id1002622538?l=en-GB Best regards
Replies
1
Boosts
0
Views
753
Activity
2w
How works Experiment (Documentation) in Swift Playground?
Experiment Create a constant with an explicit type of Float and a value of 4. https://docs.swift.org/swift-book/documentation/the-swift-programming-language/guidedtour
Replies
3
Boosts
0
Views
1.2k
Activity
1w
Swift question:
Is there a swift6 manual that will teach me how to code in swift?
Replies
4
Boosts
0
Views
202
Activity
Apr ’25
How can I enable “Approachable Concurrency” for a Swift Package?
I’m aware that Xcode version 26 beta 3 provides an option to enable Swift’s Approachable Concurrency feature at the project level. However, I’d like to achieve the same for a Swift Package. Could you please advise on how to enable Approachable Concurrency support specifically for a Swift Package?
Replies
3
Boosts
0
Views
1.1k
Activity
Jul ’25
How to retrieve the % of memory pressure using native libraries
Is there any way to retrieve the memory pressure percentage using native libraries? When I run the memory-pressure command, I can see the percentage of free memory, but I’d like to retrieve the same information using a native library.
Replies
2
Boosts
0
Views
651
Activity
Oct ’25
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!
Replies
2
Boosts
1
Views
1.6k
Activity
Nov ’25
iOS and Android
I currently have a iOS app live on the App Store but I also want to release it on Android, the whole code is in Swift so would that be possible or would I have to rewrite my whole apps code in a different coding language.
Replies
2
Boosts
0
Views
2.7k
Activity
Jan ’26
Data Disappeared
Hi, writing a database app for storing equipment details. Spent the day doing minor changes and tidying with many backups made, and always re-building to check its all working. Everything ok but then next build looses all data, what's the best thing to check to see if the data is still there, any help would be fantastic.
Replies
1
Boosts
0
Views
1.2k
Activity
3w
Apple Silicon calling printf
What is the proper way to pass arguments to printf with multiple variables using ARM64 Apple Silicon? Example: fOutputStr: .asciz "Element[%d] = %d\n" // formated output string for an output of: Element[4] = 9 This code (see below) works on Raspberry Pi 5, on my Mac Studio, I am getting this output, Element[9] = 1871655168 What do I need to do to use printf from an assembly language call with multiple variables? I am using the following code. ` .align 2 // memory alignment model for 64-bit ARMc #if defined(APPLE) .global _main // Provide program starting address to linker Mac OS _main: #else .global main // Raspian and Linux main: #endif // stack frame work setup START stp x29, x30, [sp, -16]! str x20, [sp, -16]! mov x29, sp // stack frame work setup END // setup printf call #if defined(APPLE) adrp x0, fOutputStr@PAGE add x0, x0, fOutputStr@PAGEOFF #else ldr x0, =fOutputStr #endif mov w1, #4 mov w2, #9 print_brk: #if defined(APPLE) stp X0, X1, [SP, #-16]! stp X2, X3, [SP, #-16]! bl _printf ldp X2, X3, [SP], #16 ldp X0, X1, [SP], #16 #else bl printf #endif done: // closing stack frame work ldr x20, [sp],16 ldp x29, x30, [sp],16 // exit mov w0, wzr ret .data .align 4 // intArrayPtr: .word 3,7,5,2,4,8 // word, each value is offset by 4 fOutputStr: .asciz "Element[%d] = %d\n" // formated output string
Replies
6
Boosts
1
Views
743
Activity
2w
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.
Replies
1
Boosts
6
Views
2.8k
Activity
Apr ’25
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 () -&gt; () at &lt;compiler-generated&gt;: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.
Replies
24
Boosts
7
Views
3.1k
Activity
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
Replies
6
Boosts
0
Views
3.1k
Activity
Sep ’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
Replies
23
Boosts
1
Views
34k
Activity
Oct ’25