Request notification permission iOS

AppDelegate.Swift

// displaying only relevant content not all the functions

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {

  // other stuff of didFinishLaunchingWithOptions inside app delegate

  if #available(iOS 10.0, *) {
    UNUserNotificationCenter.current().delegate = self
    let authOptions: UNAuthorizationOptions = [.alert, .badge, .sound]
    UNUserNotificationCenter.current().requestAuthorization(
      options: authOptions,
      completionHandler: {_, _ in })
  } else {
    let settings: UIUserNotificationSettings =
      UIUserNotificationSettings(types: [.alert, .badge, .sound], categories: nil)
    application.registerUserNotificationSettings(settings)
    application.registerForRemoteNotifications()
  }
  
  FirebaseApp.configure()
    
    NotificationCenter.default.addObserver(self, selector: #selector(self.tokenRefreshNotification(notification:)), name: NSNotification.Name.InstanceIDTokenRefresh, object: nil)
  
}  

func tokenRefreshNotification(notification: NSNotification) {
  let refreshedToken = InstanceID.instanceID().token()
  print("Dhruw: Connected to FCM. Token : \(String(describing: refreshedToken))")
  connectToFCM()
}

func connectToFCM() {
  Messaging.messaging().shouldEstablishDirectChannel = true
}