How to ensure the application continues to run in the background?

Various iOS mechanisms are used to ensure the app works in the background, depending on the type of task:

• Background Modes: These are predefined system modes that allow certain operations to run in the background. Common ones include:

  • audio: Playing or recording audio.
  • location: Tracking location.
  • voip: Handling VoIP calls.
  • fetch: Regularly downloading new content.
  • processing: Performing resource-intensive tasks.
  • remote-notification: Handling push notifications.

  To activate background modes, add the relevant keys to Info.plist or use Capabilities in Xcode.

• Background Task: Allows a limited amount of time to complete the current task after the app moves to the background.

  var backgroundTask: UIBackgroundTaskIdentifier = .invalid
  
  func registerBackgroundTask() {
      backgroundTask = UIApplication.shared.beginBackgroundTask {
          // Handle timeout
          self.endBackgroundTask()
      }
      // Perform background task
      // ...
  }
  
  func endBackgroundTask() {
      UIApplication.shared.endBackgroundTask(backgroundTask)
      backgroundTask = .invalid
  }
  

• Background Fetch: Allows the system to periodically launch the app in the background to check and download new content.

  // In AppDelegate, in didFinishLaunchingWithOptions
  UIApplication.shared.setMinimumBackgroundFetchInterval(UIApplication.backgroundFetchIntervalMinimum)
  
  // In didFinishLaunchingWithOptions or a separate method
  func application(_ application: UIApplication, performFetchWithCompletionHandler completionHandler: @escaping (UIBackgroundFetchResult) -> Void) {
      // Perform asynchronous data loading
      // Call completionHandler with the result:
      // .newData, .noData, .failed
      completionHandler(.newData)
  }
  

• Background Processing: Designed for executing resource-intensive tasks that may take a long time. Uses BGTaskScheduler.

  import BackgroundTasks
  
  let taskID = "com.yourapp.mytask"
  
  func registerBackgroundTasks() {
      BGTaskScheduler.shared.register(forTaskWithIdentifier: taskID) { task in
          // Execute task
          self.handleBackgroundTask(task: task as! BGProcessingTask)
      }
  }
  
  func handleBackgroundTask(task: BGProcessingTask) {
      // Perform long-running task
      // Mark task as completed
      task.setTaskCompleted(success: true)
  }
  
  // Scheduling the task
  func scheduleBackgroundProcessingTask() {
      let request = BGProcessingTaskRequest(identifier: taskID)
      // Set environment requirements (e.g., network, battery)
      request.requiresNetworkConnectivity = true
  
      do {
          try BGTaskScheduler.shared.submit(request)
      } catch {
          print("Could not schedule task: \(error)")
      }
  }
  

• Push Notifications: Silent pushes can be used to activate the app in the background and download new content.

• Work Manager (Android) equivalent for iOS (indirect): BGTaskScheduler is similar to Android's Work Manager, allowing scheduling of background tasks considering system resources and constraints.

The choice of mechanism depends on the type of task to be performed in the background. Using an inappropriate mechanism may lead to app rejection during review in the App Store and quick termination of background processes by the system. It is also important to be mindful of system resources: battery, memory, and CPU.