how to test in ios device about bgtaskscheduler function not using debug function

Question

i have no problem when using debug function in my ios device not simulator. (ex, e -l objc -- (void)[[BGTaskScheduler sharedScheduler] _simulateLaunchForTaskWithIdentifier:@"TASK_IDENTIFIER"] )

but when do not using debug function, follow my code, it will be play the music after 60 seconds going to background. however nothing to happen in the device.

how do i test the device not using debug function?

import UIKit
import BackgroundTasks
import os.log
import AVFoundation

private let logger = Logger(subsystem: Bundle.main.bundleIdentifier!, category: "AppDelegate")

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    
    let bgTaskIdentifier = "com.hakjun.bgTest.playMusic"
    var alarmTime : Int = 0
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        // Override point for customization after application launch.
        BGTaskScheduler.shared.register(forTaskWithIdentifier: bgTaskIdentifier, using: nil) { task in
            self.handleAppRefresh(task: task as! BGAppRefreshTask)
            print("test bg")
        }
        return true
    }
    
    func scheduleAppRefresh(time : Double) {
            let request = BGAppRefreshTaskRequest(identifier: bgTaskIdentifier)
            request.earliestBeginDate = Date(timeIntervalSinceNow: time)
            do {
                try BGTaskScheduler.shared.submit(request)
                print("schedule app refresh")
            } catch {
                print("Could not schedule app refresh task \(error.localizedDescription)")
            }
        }
    
    func handleAppRefresh(task : BGAppRefreshTask){
        scheduleAppRefresh(time: 60)
        let queue = OperationQueue()
        queue.maxConcurrentOperationCount = 1
        let appRefreshOperation = BlockOperation {
            Singleton.sharedInstance.play()
        }
//        queue.addOperation(appRefreshOperation)
        task.expirationHandler = {
            print("expire background")
            queue.cancelAllOperations()
        }
        let lastOperation = queue.operations.last
        lastOperation?.completionBlock = {
            task.setTaskCompleted(success: !(lastOperation?.isCancelled ?? false))
        }
        print("background handle")
        queue.addOperation(appRefreshOperation)
    }
    
    // MARK: UISceneSession Lifecycle
    
    func application(_ application: UIApplication, configurationForConnecting connectingSceneSession: UISceneSession, options: UIScene.ConnectionOptions) -> UISceneConfiguration {
        // Called when a new scene session is being created.
        // Use this method to select a configuration to create the new scene with.
        return UISceneConfiguration(name: "Default Configuration", sessionRole: connectingSceneSession.role)
    }
    
    func application(_ application: UIApplication, didDiscardSceneSessions sceneSessions: Set<UISceneSession>) {
        // Called when the user discards a scene session.
        // If any sessions were discarded while the application was not running, this will be called shortly after application:didFinishLaunchingWithOptions.
        // Use this method to release any resources that were specific to the discarded scenes, as they will not return.
    }
    
    func applicationDidEnterBackground(_ application: UIApplication) {
        print("test bg os log2")
        logger.log("App did enter background")
        scheduleAppRefresh(time: 60)
    }
}

class Singleton {
    static let sharedInstance = Singleton()
    private var player: AVAudioPlayer?
    
    func play() {
        let audioSession = AVAudioSession.sharedInstance()
        guard let url = Bundle.main.url(forResource: "alarm2", withExtension: "mp3") else { return }
        do {
            try audioSession.setCategory(.playback, mode: .default, options: [])
        } catch let error as  NSError {
            print("audioSession 설정 오류 : \(error.localizedDescription)")
        }
        
        do {
            try AVAudioSession.sharedInstance().setCategory(AVAudioSession.Category.playback)
            try AVAudioSession.sharedInstance().setActive(true)

            player = try AVAudioPlayer(contentsOf: url, fileTypeHint: AVFileType.mp3.rawValue)
            
            guard let player = player else { return }
            
            player.play()

        } catch let error {
            print(error.localizedDescription)
        }
    }

    func stop() {
        player?.stop()
    }
}

Answer 1

FYI, BGAppResfreshTask is for “updating your app with small bits of information”, i.e., for performing a small network request to refresh your app so that, when the user next launches the app, you have more current information ready and waiting for them. But this app refresh is performed at a time chosen at the discretion of the OS, based upon many factors, but not earlier than earliestBeginDate.

Thus is not appropriate for an alarm clock because (a) you are not doing a network request to refresh your app; and (b) it is not guaranteed to run at the designated “earliest” date, only some time thereafter.

You might consider scheduling a user notification, instead.

---

You asked:

how do i test the device not using debug function?

You add logging statements. But rather than using print or NSLog, one would add Logger statements as discussed in WWDC 2020 Explore logging in Swift. (Or, if supporting iOS versions prior to iOS 14, use os_log; this was described in WWDC 2016 video Unified Logging and Activity Tracing, but that video is no longer available.) These Logger/os_log logging statements issued from an iOS app can be monitored from the macOS Console app.

So, once you have added your logging messages in your code in the relevant spots, using Logger (or os_log), you can then

• install app on your device,
• connect device to your computer,
• launch the app directly from your device and
• you can watch the log statements issued by your app in your macOS Console.

See points 3 and 4 in Swift: print() vs println() vs NSLog().

But note, you do not want to run the app from Xcode. You can install it by running it from Xcode, but then stop execution and re-launch the app directly on the device, not using Xcode. Unfortunately, being attached to the Xcode debugger keeps the app artificially running in the background when it would really be otherwise suspended when running independently on the device. So, when testing background execution on a physical device, do not debug it from Xcode directly, but rather add logging statements, launch the app directly from the device, and watch the logging statements in the macOS console.

Alternatively, sometimes background processes happen hours later, so I also will occasionally write log statements to a text file in the Application Support directory, and revisit that file later (by downloading the container back to my Mac later). In the case of background fetch and background tasks (which can happen hours or days later), this can be useful. In the case of an alarm app, though, the macOS Console approach outlined above is easiest.