Processes & Concurrency

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Concurrency Documentation

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How do I internally handle conditionally conforming to ConnectablePublisher
I'm making an operator Publisher, which has to wrap the upstream publisher. But I want the operator to conditionally conform to ConnectablePublisher, but only when the upstream publisher does the same. I can make my connect() call the upstream's connect(), but is that all I have to do? That Apple's plumbing will automatically hold back the initial call to the Subscription object if the publisher is connectable. Otherwise, I need to make a flag in the subscription for when to connect, which would involve an infinitely copyable struct somehow send a message to a unique class/actor. That last part makes sense to me, but it also seems like too much work for something plug-and-play. Having Apple's implementation taking care of that issue also makes sense, and would be a better solution.
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159
Jan ’26
BGProcessingTask Not Triggering at Scheduled Time After Updating to Xcode 26.1.1
I’m reaching out regarding an issue we’ve been experiencing with BGProcessingTask since upgrading to Xcode 26.1.1. Issue Summary Our daily background processing task—scheduled shortly after end‑of‑day—has stopped triggering reliably at night. This behavior started occurring only after updating to Xcode 26.1.1. Prior to this update, the task consistently ran around midnight, executed for ~10–15 seconds, and successfully rescheduled itself for the next day. Expected Behavior BGProcessingTask should run at/near the scheduled earliestBeginDate, which we set to roughly 2 hours after end-of-day. The task should execute, complete, and then reschedule itself. Actual Behavior On devices running builds compiled with Xcode 26.1.1, the task does not trigger at all during the night. The same code worked reliably before the Xcode update. No system logs indicate rejection, expiration, or background task denial. Technical Details This is the identifier we use: private enum DayEndProcessorConst {    static let taskIdentifier = "com.company.sdkmanagement.daysummary.manager" } The task is registered as follows: When app launched BGTaskScheduler.shared.register(    forTaskWithIdentifier: DayEndProcessorConst.taskIdentifier,    using: nil ) { [weak self] task in    self?.handleDayEndTask(task) } And scheduled like this: let date = Calendar.current.endOfDay(for: Date()).addingTimeInterval(60 * 60 * 2) let request = BGProcessingTaskRequest(identifier: DayEndProcessorConst.taskIdentifier) request.requiresNetworkConnectivity = true request.requiresExternalPower = false request.earliestBeginDate = date try BGTaskScheduler.shared.submit(request) As per our logs, tasks scheduled successfully The handler wraps the work in an operation queue, begins a UI background task, and marks completion appropriately: task.setTaskCompleted(success: true) Could you please advise whether: There are known issues with BGProcessingTask scheduling or midnight execution in Xcode 26.1.1 or iOS versions associated with it? Any new entitlement, configuration, or scheduler behavior has changed in recent releases? Additional logging or diagnostics can help pinpoint why the scheduler never fires the task?
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170
Jan ’26
Misusing a Mutex
This is a successor to: https://aninterestingwebsite.com/forums/thread/814231 I went into a slightly different direction. I generated more AI slop that use NSLock. Then I had the NSLock usage changed to Mutex usage. Now it crashes with: Task 13: EXC_BREAKPOINT (code=1, subcode=0x18d29326c) On one of the mutex closures. With an extended description: warning: TypeSystemSwiftTypeRef::operator(): had to engage SwiftASTContext fallback for type $s7Combine10PublishersO21LineBreakingPublisherE11SplitAtZeroV12Subscription33_D18F5AAE73662968F407B0A79FBD1F8DLLCy_x_qd__GD I put the class, a Subscription nested in its corresponding Publisher operator, in the given file Subscription.txt
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178
Feb ’26
Unable to set subtitle when BGContinuedProcessingTask expires
Hi, I've now identified a few areas when BGContinuedProcessingTask gets expired by the system no progress for ~30 seconds high CPU usage high temperature Some of these I can preempt and expire preemptively and handle the notification, others I cannot and just need to let the failure bubble up. When the failure does bubble up, I'd like to update the title and subtitle. I'm able to update the title, but the subtitle is fixed at "Task Failed" Is there any workaround? Or shall I file a bug here?
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144
Feb ’26
app background launch unexpectedly
Our app will launch automatically in the background,Doubt is the result of background fetch ,so we cancel the background modes setting of the background fetch,but we still can see the performFetchWithCompletionHandler method called when app launch in the background。Background launch will cause some bugs in our app. We don't want the app to start in the background. We hope to get help
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838
Dec ’25
Called endBackgroundTask but not working
When my app enter to background, I start a background task, and when Expiration happens, I end my background task. The code likes below: backgroundTask = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{ dispatch_async(dispatch_get_main_queue(), ^{ if (backgroundTask != UIBackgroundTaskInvalid) { [[UIApplication sharedApplication] endBackgroundTask:backgroundTask]; backgroundTask = UIBackgroundTaskInvalid; [self cancel]; } }); }]; When the breakpoint is triggered at the endBackgroundTask line, I also get the following log: [BackgroundTask] Background task still not ended after expiration handlers were called: <UIBackgroundTaskInfo: 0x282d7ab40>: taskID = 36, taskName = Called by MyApp, from MyMethod, creationTime = 892832 (elapsed = 26). This app will likely be terminated by the system. Call UIApplication.endBackgroundTask(:) to avoid this. The log don't appear every time, so why is that? Is there something wrong with my code?
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3.1k
Jun ’25
Sensorkit - Troubleshooting SRErrorDataInaccessible in Background Fetch with SensorKit
Hello, I am currently developing an iOS application using SensorKit. I encountered an issue when attempting to fetch SensorKit data in the background using background tasks (appRefresh, processing). The following error occurs: In the delegate function func sensorReader(_ reader: SRSensorReader, fetching fetchRequest: SRFetchRequest, failedWithError error: any Error) {}, I receive the error: SRErrorDataInaccessible. In code specific manner: start and handle background fetch (appRefresh) func handleAppRefreshTask(task: BGAppRefreshTask) { logger.logWithServer(level: .default, message: "background fetch start", category: String(describing: BackgroundTaskManager.self)) scheduleBackgroundFetch() let queue = OperationQueue() queue.maxConcurrentOperationCount = 1 let fetchOperation = FetchOperation() queue.addOperation(fetchOperation) task.expirationHandler = { self.logger.logWithServer(level: .error, message: "background fetch expirated", category: String(describing: BackgroundTaskManager.self)) queue.cancelAllOperations() } fetchOperation.completionBlock = { task.setTaskCompleted(success: !fetchOperation.isCancelled) } } Background fetch operation class class FetchOperation: Operation { override func main() { guard !isCancelled else { return } Task { // this function will execute fetch request for all user allowed sensorReader, 'func fetch(_ request: SRFetchRequest)' await SensorkitManager.shared.startFetchAndUpload() } } } I have the following questions: Is it possible to fetch SensorKit data in the background? If it is possible, why does the above error occur? If it is possible, could you provide the solution code and the correct workflow to avoid this error? Thank you.
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1.2k
Feb ’26
How to correctly deploy bundled launchdaemons/launchagents?
I'm working on an enterprise product that's mainly a daemon (with Endpoint Security) without any GUI component. I'm looking into the update process for daemons/agents that was introduced with Ventura (Link), but I have to say that the entire process is just deeply unfun. Really can't stress this enough how unfun. Anyway... The product bundle now contains a dedicated Swift executable that calls SMAppService.register for both the daemon and agent. It registers the app in the system preferences login items menu, but I also get an error. Error registering daemon: Error Domain=SMAppServiceErrorDomain Code=1 "Operation not permitted" UserInfo={NSLocalizedFailureReason=Operation not permitted} What could be the reason? I wouldn't need to activate the items, I just need them to be added to the list, so that I can control them via launchctl. Which leads me to my next question, how can I control bundled daemons/agents via launchctl? I tried to use launchctl enable and bootstrap, just like I do with daemons under /Library/LaunchDaemons, but all I get is sudo launchctl enable system/com.identifier.daemon sudo launchctl bootstrap /Path/to/daemon/launchdplist/inside/bundle/Library/LaunchDaemons/com.blub.plist Bootstrap failed: 5: Input/output error (not super helpful error message) I'm really frustrated by the complexity of this process and all of its pitfalls.
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1.1k
Aug ’25
macOS 14 XPC vs Foundation XPC
I'm looking into a newer XPC API available starting with macOS 14. Although it's declared as a low-level API I can't figure it how to specify code signing requirement using XPCListener and XPCSession. How do I connect it with xpc_listener_set_peer_code_signing_requirement and xpc_connection_set_peer_code_signing_requirement which require xpc_listener_t and xpc_connection_t respectively? Foundation XPC is declared as a high-level API and provides easy ways to specify code signing requirements on both ends of xpc. I'm confused with all these XPC APIs and their future: Newer really high-level XPCListener and XPCSession API (in low-level framework???) Low-level xpc_listener_t & xpc_connection_t -like API. Is it being replaced by newer XPCListener and XPCSession? How is it related to High-level Foundation XPC? Are NSXPCListener and NSXPCConnection going to be deprecated and replaced by XPCListener and XPCSession??
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845
Aug ’25
Some fundamental doubts about DisptachQueue and GCD
I understand that GCD and it's underlying implementations have evolved over time. And many things have not been shared explicitly in Apple documentation. The most concepts of DispatchQueue (serial and concurrent queues), DispatchQoS, target queue and system provided queues: main and globals etc. I have some doubts & questions to clarify: [Main Dispatch Queue] [Link] Because the main queue doesn't behave entirely like a regular serial queue, it may have unwanted side-effects when used in processes that are not UI apps (daemons). For such processes, the main queue should be avoided. What does it mean? Can you elaborate? [Global Concurrent Dispatch Queues] Are they global to a process or across processes on a device. I believe it is the first case but just wanted to be sure. [Global Concurrent Dispatch Queues] Does system create 4 (for each QoS) * 2 (over-commiting and non-overcommiting queues) = 8 queues in all. When does which type of queue comes into play? [Custom Queue][Target Queue concept] [swift-corelibs-libdispatch/man/dispatch_queue_create.3] QUOTE The default target queue of all dispatch objects created by the application is the default priority global concurrent queue. UNQUOTE Is this stil true? We could not find a mention of this in any latest official apple documentation (though some old forum threads (one more) and github code documentation indicate the same). The official documentation only says: [dispatch_set_target_queue] QUOTE If you want the system to provide a queue that is appropriate for the current object UNQUOTE [dispatch_queue_create_with_target] QUOTE Specify DISPATCH_TARGET_QUEUE_DEFAULT to set the target queue to the default type for the current dispatch queue.UNQUOTE [Dispatch>DispatchQueue>init] QUOTE Specify DISPATCH_TARGET_QUEUE_DEFAULT if you want the system to provide a queue that is appropriate for the current object. UNQUOTE What is the difference between passing target queue as 'nil' vs 'DISPATCH_TARGET_QUEUE_DEFAULT' to DispatchQueue init? [Custom Queue][Target Queue concept] [dispatch_set_target_queue] QUOTE The system doesn't allocate threads to the dispatch queue if it has a target queue, unless that target queue is a global concurrent queue. UNQUOTE The system does allocate threads to the custom dispatch queues that have global concurrent queue as the default target. What does that mean? Why does targetting to global concurrent queues mean in that case? [System / GCD Thread Pool] that excutes work items from DispatchQueue: Is this thread pool per queue? or across queues per process? or across processes per device?
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1.4k
Jan ’26
What DispatchQueues should i use for my app's communication subsystem?
We would be creating N NWListener objects and M NWConnection objects in our process' communication subsystem to create server sockets, accepted client sockets on server and client sockets on clients. Both NWConnection and NWListener rely on DispatchQueue to deliver state changes, incoming connections, send/recv completions etc. What DispatchQueues should I use and why? Global Concurrent Dispatch Queue (and which QoS?) for all NWConnection and NWListener One custom concurrent queue (which QoS?) for all NWConnection and NWListener? (Does that anyways get targetted to one of the global queues?) One custom concurrent queue per NWConnection and NWListener though all targetted to Global Concurrent Dispatch Queue (and which QoS?)? One custom concurrent queue per NWConnection and NWListener though all targetted to single target custom concurrent queue? For every option above, how am I impacted in terms of parallelism, concurrency, throughput &amp; latency and how is overall system impacted (with other processes also running)? Seperate questions (sorry for the digression): Are global concurrent queues specific to a process or shared across all processes on a device? Can I safely use setSpecific on global dispatch queues in our app?
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1.2k
Jan ’26
Background Audio Recording
I have an app that uses background audio recording. From what others say, I have enabled the audio background mode to keep the audio session active, and this worked. But when submitting the app to the app store, the app was rejected because the audio background mode is only supposed to be used for audio playback. How do I create this background mode while following Apple's guidelines?
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307
Jan ’26
Service Showing "Not Responding" in Activity Monitor Despite Running Threads.
I am encountering an issue with my application, BloxOneEndpoint.pkg, which includes two services: rc_service_infoblox – Runs as the root user. Controller Application – Runs as a normal user. Although a thread within rc_service_infoblox is running fine and performing its expected tasks, I notice that the service appears as "Not Responding" in Activity Monitor. Despite normal functionality, this status is concerning, as it may indicate some issue to customer. I would appreciate any insights into why this might be happening and how to resolve it. Is there a specific API or mechanism I should use to ensure the service remains in a "Running" state in Activity Monitor? Thank you for your guidance.
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373
Apr ’25
Launch Host App from Share Extension
Hi! Could you please point me to the official documentation or recommended approach for launching the host app from a Share Extension? The scenario is: The user is sharing some text to my app. I need launch App and show this text. At the moment, I'm using the following hack: let selector = NSSelectorFromString("sharedApplication") if let app = UIApplication.perform(selector)?.takeUnretainedValue() as? UIApplication, app.responds(to: #selector(UIApplication.open(_:options:completionHandler:))) { app.open(url, options: [:], completionHandler: nil) } This does work, but it's terrible. So, the question: What is the official way to open the host app from within a Share Extension? Thanks!
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182
Apr ’25
Working with Input/Output stream with Swift 6 and concurrency framework
Hello, I am developing an application which is communicating with external device using BLE and L2CAP. I wonder what are the best practices of using Input & Output streams that are established with L2CAP connection when working with Swift 6 concurrency model. I've been trying to find some examples and hints for some time now but unfortunately there isn't much available. One useful thread I've found is: https://aninterestingwebsite.com/forums/thread/756281 but it does not offer much insight into using eg. actor model with streams. I wonder if something has changed in this regards? Also, are there any plans to migrate eg. CoreBluetooth stack to new swift 6 concurrency ?
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171
Apr ’25
Return the results of a Spotlight query synchronously from a Swift function
How can I return the results of a Spotlight query synchronously from a Swift function? I want to return a [String] that contains the items that match the query, one item per array element. I specifically want to find all data for Spotlight items in the /Applications folder that have a kMDItemAppStoreAdamID (if there is a better predicate than kMDItemAppStoreAdamID > 0, please let me know). The following should be the correct query: let query = NSMetadataQuery() query.predicate = NSPredicate(format: "kMDItemAppStoreAdamID > 0") query.searchScopes = ["/Applications"] I would like to do this for code that can run on macOS 10.13+, which precludes using Swift Concurrency. My project already uses the latest PromiseKit, so I assume that the solution should use that. A bonus solution using Swift Concurrency wouldn't hurt as I will probably switch over sometime in the future, but won't be able to switch soon. I have written code that can retrieve the Spotlight data as the [String], but I don't know how to return it synchronously from a function; whatever I tried, the query hangs, presumably because I've called various run loop functions at the wrong places. In case it matters, the app is a macOS command-line app using Swift 5.7 & Swift Argument Parser 1.5.0. The Spotlight data will be output only as text to stdout & stderr, not to any Apple UI elements.
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204
Apr ’25
iOS BGTaskScheduler
Hi! I'm trying to submit a task request into BGTaskScheduler when I background my app. The backgrounding triggers an update of data to a shared app groups container. I'm currently getting the following error and unsure where it's coming from: *** Assertion failure in -[BGTaskScheduler _unsafe_submitTaskRequest:error:], BGTaskScheduler.m:274 Here is my code: BGAppRefreshTaskRequest *request = [[BGAppRefreshTaskRequest alloc] initWithIdentifier:kRBBackgroundTaskIdentifier]; NSError *error = nil; bool success = [[BGTaskScheduler sharedScheduler] submitTaskRequest:request error:&error];
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201
Apr ’25
APP Background Keep-Alive
Dear Apple: We are developing an app for file sharing between mobile devices. We want to create an iOS app that can continue sharing files with other devices even when it is running in the background. We are using WLAN channels for file sharing. Could you please advise on which background persistence measures we should use to ensure the iOS app can maintain file transfer when it goes to the background? Thank you.
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177
Apr ’25
How do I internally handle conditionally conforming to ConnectablePublisher
I'm making an operator Publisher, which has to wrap the upstream publisher. But I want the operator to conditionally conform to ConnectablePublisher, but only when the upstream publisher does the same. I can make my connect() call the upstream's connect(), but is that all I have to do? That Apple's plumbing will automatically hold back the initial call to the Subscription object if the publisher is connectable. Otherwise, I need to make a flag in the subscription for when to connect, which would involve an infinitely copyable struct somehow send a message to a unique class/actor. That last part makes sense to me, but it also seems like too much work for something plug-and-play. Having Apple's implementation taking care of that issue also makes sense, and would be a better solution.
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0
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159
Activity
Jan ’26
Missing Bluetooth background mode
I built an iOS app and debugged it using my iPhone 11. It works fine. My app uses Bluetooth because the physical data logger reads data via Bluetooth. I published it to the Apple store. After installing it on the iPhone 13 pro. The app works, but the device is not selected.
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0
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133
Activity
Jan ’26
BGProcessingTask Not Triggering at Scheduled Time After Updating to Xcode 26.1.1
I’m reaching out regarding an issue we’ve been experiencing with BGProcessingTask since upgrading to Xcode 26.1.1. Issue Summary Our daily background processing task—scheduled shortly after end‑of‑day—has stopped triggering reliably at night. This behavior started occurring only after updating to Xcode 26.1.1. Prior to this update, the task consistently ran around midnight, executed for ~10–15 seconds, and successfully rescheduled itself for the next day. Expected Behavior BGProcessingTask should run at/near the scheduled earliestBeginDate, which we set to roughly 2 hours after end-of-day. The task should execute, complete, and then reschedule itself. Actual Behavior On devices running builds compiled with Xcode 26.1.1, the task does not trigger at all during the night. The same code worked reliably before the Xcode update. No system logs indicate rejection, expiration, or background task denial. Technical Details This is the identifier we use: private enum DayEndProcessorConst {    static let taskIdentifier = "com.company.sdkmanagement.daysummary.manager" } The task is registered as follows: When app launched BGTaskScheduler.shared.register(    forTaskWithIdentifier: DayEndProcessorConst.taskIdentifier,    using: nil ) { [weak self] task in    self?.handleDayEndTask(task) } And scheduled like this: let date = Calendar.current.endOfDay(for: Date()).addingTimeInterval(60 * 60 * 2) let request = BGProcessingTaskRequest(identifier: DayEndProcessorConst.taskIdentifier) request.requiresNetworkConnectivity = true request.requiresExternalPower = false request.earliestBeginDate = date try BGTaskScheduler.shared.submit(request) As per our logs, tasks scheduled successfully The handler wraps the work in an operation queue, begins a UI background task, and marks completion appropriately: task.setTaskCompleted(success: true) Could you please advise whether: There are known issues with BGProcessingTask scheduling or midnight execution in Xcode 26.1.1 or iOS versions associated with it? Any new entitlement, configuration, or scheduler behavior has changed in recent releases? Additional logging or diagnostics can help pinpoint why the scheduler never fires the task?
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1
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170
Activity
Jan ’26
Misusing a Mutex
This is a successor to: https://aninterestingwebsite.com/forums/thread/814231 I went into a slightly different direction. I generated more AI slop that use NSLock. Then I had the NSLock usage changed to Mutex usage. Now it crashes with: Task 13: EXC_BREAKPOINT (code=1, subcode=0x18d29326c) On one of the mutex closures. With an extended description: warning: TypeSystemSwiftTypeRef::operator(): had to engage SwiftASTContext fallback for type $s7Combine10PublishersO21LineBreakingPublisherE11SplitAtZeroV12Subscription33_D18F5AAE73662968F407B0A79FBD1F8DLLCy_x_qd__GD I put the class, a Subscription nested in its corresponding Publisher operator, in the given file Subscription.txt
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1
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178
Activity
Feb ’26
Unable to set subtitle when BGContinuedProcessingTask expires
Hi, I've now identified a few areas when BGContinuedProcessingTask gets expired by the system no progress for ~30 seconds high CPU usage high temperature Some of these I can preempt and expire preemptively and handle the notification, others I cannot and just need to let the failure bubble up. When the failure does bubble up, I'd like to update the title and subtitle. I'm able to update the title, but the subtitle is fixed at "Task Failed" Is there any workaround? Or shall I file a bug here?
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0
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144
Activity
Feb ’26
app background launch unexpectedly
Our app will launch automatically in the background,Doubt is the result of background fetch ,so we cancel the background modes setting of the background fetch,but we still can see the performFetchWithCompletionHandler method called when app launch in the background。Background launch will cause some bugs in our app. We don't want the app to start in the background. We hope to get help
Replies
4
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0
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838
Activity
Dec ’25
Called endBackgroundTask but not working
When my app enter to background, I start a background task, and when Expiration happens, I end my background task. The code likes below: backgroundTask = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{ dispatch_async(dispatch_get_main_queue(), ^{ if (backgroundTask != UIBackgroundTaskInvalid) { [[UIApplication sharedApplication] endBackgroundTask:backgroundTask]; backgroundTask = UIBackgroundTaskInvalid; [self cancel]; } }); }]; When the breakpoint is triggered at the endBackgroundTask line, I also get the following log: [BackgroundTask] Background task still not ended after expiration handlers were called: <UIBackgroundTaskInfo: 0x282d7ab40>: taskID = 36, taskName = Called by MyApp, from MyMethod, creationTime = 892832 (elapsed = 26). This app will likely be terminated by the system. Call UIApplication.endBackgroundTask(:) to avoid this. The log don't appear every time, so why is that? Is there something wrong with my code?
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3
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3.1k
Activity
Jun ’25
Sensorkit - Troubleshooting SRErrorDataInaccessible in Background Fetch with SensorKit
Hello, I am currently developing an iOS application using SensorKit. I encountered an issue when attempting to fetch SensorKit data in the background using background tasks (appRefresh, processing). The following error occurs: In the delegate function func sensorReader(_ reader: SRSensorReader, fetching fetchRequest: SRFetchRequest, failedWithError error: any Error) {}, I receive the error: SRErrorDataInaccessible. In code specific manner: start and handle background fetch (appRefresh) func handleAppRefreshTask(task: BGAppRefreshTask) { logger.logWithServer(level: .default, message: "background fetch start", category: String(describing: BackgroundTaskManager.self)) scheduleBackgroundFetch() let queue = OperationQueue() queue.maxConcurrentOperationCount = 1 let fetchOperation = FetchOperation() queue.addOperation(fetchOperation) task.expirationHandler = { self.logger.logWithServer(level: .error, message: "background fetch expirated", category: String(describing: BackgroundTaskManager.self)) queue.cancelAllOperations() } fetchOperation.completionBlock = { task.setTaskCompleted(success: !fetchOperation.isCancelled) } } Background fetch operation class class FetchOperation: Operation { override func main() { guard !isCancelled else { return } Task { // this function will execute fetch request for all user allowed sensorReader, 'func fetch(_ request: SRFetchRequest)' await SensorkitManager.shared.startFetchAndUpload() } } } I have the following questions: Is it possible to fetch SensorKit data in the background? If it is possible, why does the above error occur? If it is possible, could you provide the solution code and the correct workflow to avoid this error? Thank you.
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3
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1.2k
Activity
Feb ’26
How to correctly deploy bundled launchdaemons/launchagents?
I'm working on an enterprise product that's mainly a daemon (with Endpoint Security) without any GUI component. I'm looking into the update process for daemons/agents that was introduced with Ventura (Link), but I have to say that the entire process is just deeply unfun. Really can't stress this enough how unfun. Anyway... The product bundle now contains a dedicated Swift executable that calls SMAppService.register for both the daemon and agent. It registers the app in the system preferences login items menu, but I also get an error. Error registering daemon: Error Domain=SMAppServiceErrorDomain Code=1 "Operation not permitted" UserInfo={NSLocalizedFailureReason=Operation not permitted} What could be the reason? I wouldn't need to activate the items, I just need them to be added to the list, so that I can control them via launchctl. Which leads me to my next question, how can I control bundled daemons/agents via launchctl? I tried to use launchctl enable and bootstrap, just like I do with daemons under /Library/LaunchDaemons, but all I get is sudo launchctl enable system/com.identifier.daemon sudo launchctl bootstrap /Path/to/daemon/launchdplist/inside/bundle/Library/LaunchDaemons/com.blub.plist Bootstrap failed: 5: Input/output error (not super helpful error message) I'm really frustrated by the complexity of this process and all of its pitfalls.
Replies
7
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1.1k
Activity
Aug ’25
macOS 14 XPC vs Foundation XPC
I'm looking into a newer XPC API available starting with macOS 14. Although it's declared as a low-level API I can't figure it how to specify code signing requirement using XPCListener and XPCSession. How do I connect it with xpc_listener_set_peer_code_signing_requirement and xpc_connection_set_peer_code_signing_requirement which require xpc_listener_t and xpc_connection_t respectively? Foundation XPC is declared as a high-level API and provides easy ways to specify code signing requirements on both ends of xpc. I'm confused with all these XPC APIs and their future: Newer really high-level XPCListener and XPCSession API (in low-level framework???) Low-level xpc_listener_t & xpc_connection_t -like API. Is it being replaced by newer XPCListener and XPCSession? How is it related to High-level Foundation XPC? Are NSXPCListener and NSXPCConnection going to be deprecated and replaced by XPCListener and XPCSession??
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2
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845
Activity
Aug ’25
Some fundamental doubts about DisptachQueue and GCD
I understand that GCD and it's underlying implementations have evolved over time. And many things have not been shared explicitly in Apple documentation. The most concepts of DispatchQueue (serial and concurrent queues), DispatchQoS, target queue and system provided queues: main and globals etc. I have some doubts & questions to clarify: [Main Dispatch Queue] [Link] Because the main queue doesn't behave entirely like a regular serial queue, it may have unwanted side-effects when used in processes that are not UI apps (daemons). For such processes, the main queue should be avoided. What does it mean? Can you elaborate? [Global Concurrent Dispatch Queues] Are they global to a process or across processes on a device. I believe it is the first case but just wanted to be sure. [Global Concurrent Dispatch Queues] Does system create 4 (for each QoS) * 2 (over-commiting and non-overcommiting queues) = 8 queues in all. When does which type of queue comes into play? [Custom Queue][Target Queue concept] [swift-corelibs-libdispatch/man/dispatch_queue_create.3] QUOTE The default target queue of all dispatch objects created by the application is the default priority global concurrent queue. UNQUOTE Is this stil true? We could not find a mention of this in any latest official apple documentation (though some old forum threads (one more) and github code documentation indicate the same). The official documentation only says: [dispatch_set_target_queue] QUOTE If you want the system to provide a queue that is appropriate for the current object UNQUOTE [dispatch_queue_create_with_target] QUOTE Specify DISPATCH_TARGET_QUEUE_DEFAULT to set the target queue to the default type for the current dispatch queue.UNQUOTE [Dispatch>DispatchQueue>init] QUOTE Specify DISPATCH_TARGET_QUEUE_DEFAULT if you want the system to provide a queue that is appropriate for the current object. UNQUOTE What is the difference between passing target queue as 'nil' vs 'DISPATCH_TARGET_QUEUE_DEFAULT' to DispatchQueue init? [Custom Queue][Target Queue concept] [dispatch_set_target_queue] QUOTE The system doesn't allocate threads to the dispatch queue if it has a target queue, unless that target queue is a global concurrent queue. UNQUOTE The system does allocate threads to the custom dispatch queues that have global concurrent queue as the default target. What does that mean? Why does targetting to global concurrent queues mean in that case? [System / GCD Thread Pool] that excutes work items from DispatchQueue: Is this thread pool per queue? or across queues per process? or across processes per device?
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1.4k
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Jan ’26
What DispatchQueues should i use for my app's communication subsystem?
We would be creating N NWListener objects and M NWConnection objects in our process' communication subsystem to create server sockets, accepted client sockets on server and client sockets on clients. Both NWConnection and NWListener rely on DispatchQueue to deliver state changes, incoming connections, send/recv completions etc. What DispatchQueues should I use and why? Global Concurrent Dispatch Queue (and which QoS?) for all NWConnection and NWListener One custom concurrent queue (which QoS?) for all NWConnection and NWListener? (Does that anyways get targetted to one of the global queues?) One custom concurrent queue per NWConnection and NWListener though all targetted to Global Concurrent Dispatch Queue (and which QoS?)? One custom concurrent queue per NWConnection and NWListener though all targetted to single target custom concurrent queue? For every option above, how am I impacted in terms of parallelism, concurrency, throughput &amp; latency and how is overall system impacted (with other processes also running)? Seperate questions (sorry for the digression): Are global concurrent queues specific to a process or shared across all processes on a device? Can I safely use setSpecific on global dispatch queues in our app?
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13
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1.2k
Activity
Jan ’26
Background terminations increase
We've seen a recent increase in background terminations: blue - System Pressure orange - Task Timeout I'm trying to understand the increase in system-pressure terminations, since there's no corresponding increase in memory at suspension. Are there other system resources for which iOS will terminate an app?
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3
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282
Activity
Jun ’25
Background Audio Recording
I have an app that uses background audio recording. From what others say, I have enabled the audio background mode to keep the audio session active, and this worked. But when submitting the app to the app store, the app was rejected because the audio background mode is only supposed to be used for audio playback. How do I create this background mode while following Apple's guidelines?
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4
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307
Activity
Jan ’26
Service Showing "Not Responding" in Activity Monitor Despite Running Threads.
I am encountering an issue with my application, BloxOneEndpoint.pkg, which includes two services: rc_service_infoblox – Runs as the root user. Controller Application – Runs as a normal user. Although a thread within rc_service_infoblox is running fine and performing its expected tasks, I notice that the service appears as "Not Responding" in Activity Monitor. Despite normal functionality, this status is concerning, as it may indicate some issue to customer. I would appreciate any insights into why this might be happening and how to resolve it. Is there a specific API or mechanism I should use to ensure the service remains in a "Running" state in Activity Monitor? Thank you for your guidance.
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13
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373
Activity
Apr ’25
Launch Host App from Share Extension
Hi! Could you please point me to the official documentation or recommended approach for launching the host app from a Share Extension? The scenario is: The user is sharing some text to my app. I need launch App and show this text. At the moment, I'm using the following hack: let selector = NSSelectorFromString("sharedApplication") if let app = UIApplication.perform(selector)?.takeUnretainedValue() as? UIApplication, app.responds(to: #selector(UIApplication.open(_:options:completionHandler:))) { app.open(url, options: [:], completionHandler: nil) } This does work, but it's terrible. So, the question: What is the official way to open the host app from within a Share Extension? Thanks!
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2
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182
Activity
Apr ’25
Working with Input/Output stream with Swift 6 and concurrency framework
Hello, I am developing an application which is communicating with external device using BLE and L2CAP. I wonder what are the best practices of using Input & Output streams that are established with L2CAP connection when working with Swift 6 concurrency model. I've been trying to find some examples and hints for some time now but unfortunately there isn't much available. One useful thread I've found is: https://aninterestingwebsite.com/forums/thread/756281 but it does not offer much insight into using eg. actor model with streams. I wonder if something has changed in this regards? Also, are there any plans to migrate eg. CoreBluetooth stack to new swift 6 concurrency ?
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2
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171
Activity
Apr ’25
Return the results of a Spotlight query synchronously from a Swift function
How can I return the results of a Spotlight query synchronously from a Swift function? I want to return a [String] that contains the items that match the query, one item per array element. I specifically want to find all data for Spotlight items in the /Applications folder that have a kMDItemAppStoreAdamID (if there is a better predicate than kMDItemAppStoreAdamID > 0, please let me know). The following should be the correct query: let query = NSMetadataQuery() query.predicate = NSPredicate(format: "kMDItemAppStoreAdamID > 0") query.searchScopes = ["/Applications"] I would like to do this for code that can run on macOS 10.13+, which precludes using Swift Concurrency. My project already uses the latest PromiseKit, so I assume that the solution should use that. A bonus solution using Swift Concurrency wouldn't hurt as I will probably switch over sometime in the future, but won't be able to switch soon. I have written code that can retrieve the Spotlight data as the [String], but I don't know how to return it synchronously from a function; whatever I tried, the query hangs, presumably because I've called various run loop functions at the wrong places. In case it matters, the app is a macOS command-line app using Swift 5.7 & Swift Argument Parser 1.5.0. The Spotlight data will be output only as text to stdout & stderr, not to any Apple UI elements.
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1
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204
Activity
Apr ’25
iOS BGTaskScheduler
Hi! I'm trying to submit a task request into BGTaskScheduler when I background my app. The backgrounding triggers an update of data to a shared app groups container. I'm currently getting the following error and unsure where it's coming from: *** Assertion failure in -[BGTaskScheduler _unsafe_submitTaskRequest:error:], BGTaskScheduler.m:274 Here is my code: BGAppRefreshTaskRequest *request = [[BGAppRefreshTaskRequest alloc] initWithIdentifier:kRBBackgroundTaskIdentifier]; NSError *error = nil; bool success = [[BGTaskScheduler sharedScheduler] submitTaskRequest:request error:&error];
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7
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201
Activity
Apr ’25
APP Background Keep-Alive
Dear Apple: We are developing an app for file sharing between mobile devices. We want to create an iOS app that can continue sharing files with other devices even when it is running in the background. We are using WLAN channels for file sharing. Could you please advise on which background persistence measures we should use to ensure the iOS app can maintain file transfer when it goes to the background? Thank you.
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1
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177
Activity
Apr ’25