Background Modes - toant-dev/toandev.github.io GitHub Wiki

func registerBackgroundTask() {
  backgroundTask = UIApplication.shared.beginBackgroundTask { [weak self] in
    self?.endBackgroundTask()
  }
  assert(backgroundTask != .invalid)
}
  
func endBackgroundTask() {
  print("Background task ended.")
  UIApplication.shared.endBackgroundTask(backgroundTask)
  backgroundTask = .invalid
}

Setting Up a Background Fetch

In order to implement background fetch, there are three things you must do:

Check the box Background fetch in the Background Modes of your app’s Capabilities. Use setMinimumBackgroundFetchInterval(:) to set a time interval appropriate for your app. Implement application(:performFetchWithCompletionHandler:) in your app delegate to handle the background fetch.

UIApplication.shared.setMinimumBackgroundFetchInterval(
  UIApplication.backgroundFetchIntervalMinimum)

// Support for background fetch
func application(
  _ application: UIApplication, 
  performFetchWithCompletionHandler 
    completionHandler: @escaping (UIBackgroundFetchResult) -> Void) {
  //1
  if let tabBarController = window?.rootViewController as? UITabBarController,
    let viewControllers = tabBarController.viewControllers {

    //2
    for viewController in viewControllers {
      if let fetchViewController = viewController as? FetchViewController {
        //3
        fetchViewController.fetch {
          //4
          fetchViewController.updateUI()
          completionHandler(.newData)
        }
      }
    }
  }
}