open specific view controller upon tapping local notification

Question

title says it all. i've went through a number of posts trying to put together a solution but to no luck..

i have a notification whose name i'm not sure of...

let request = UNNotificationRequest(identifier: "timerDone", content: content, trigger: trigger)

q1: is the name timerDone?

in viewDidLoad():

NotificationCenter.default.addObserver(self,
                                                         selector: "SomeNotificationAct:",
                                                         name: NSNotification.Name(rawValue: "timerDone"),
                                                         object: nil)

and then i have this method:

@objc func SomeNotificationAct(notification: NSNotification){
        DispatchQueue.main.async() {
            self.performSegue(withIdentifier: "NotificationView", sender: self)
        }
    }

with this in AppDelegate.swift:

private func application(application: UIApplication, didReceiveRemoteNotification userInfo: Any?){

    NotificationCenter.default.post(name: NSNotification.Name(rawValue: "SomeNotification"), object:nil)
}

any ideas how to do this? thanks in advance!

UPDATE: @Sh_Khan

first, i am coding in swift, i tried translating your code from obj-c to swift as:

if (launchOptions![UIApplicationLaunchOptionsKey.localNotification] != nil)
{
    var notification =
        launchOptions![UIApplicationLaunchOptionsKey.localNotification]
    [self application:application didReceiveLocalNotification:notification]; //how to translate?
}

what should the last line be translated into?

when you wrote:

should store a boolean variable in user defaults in didReceiveLocalNotification method and check it in viewDidAppear method of the rootViewcontroller to make the segue and then make it false as the notificationCenter will work only when app is in foreground or in background if it's not yet suspended

let's say the boolean is notiView and we set it to true when we received the local notification and thus the segue will be to a different view controller. is this what you mean?

Answer 1

I found the documentation for user notification a bit confusing and incomplete. The tutorials are better than most other Apple frameworks. However, the tutorials are mostly incomplete and assume that every app implement the notification center delegate inside the AppDelegate. Not!

For many apps handling the notification delegate in a view controller (instead of in the AppDelegate), the view controller would need to be set as the user notification center delegate inside the AppDelegate didFinishLaunchingWithOptions method. Otherwise, your notification firing would not be visible to the notification delegate when your app is launched from the background mode. Your view controller is loaded after the notification fires. You need a way to launch the delegate methods after your view controller has completed its loading.

For example: suppose you are using a split view controller as your initial view controller for your app and you have implemented the split VC's master view controller as your notification delegate, you would need to let UNUserNotificationCenter know that the master VC is its delegate when your application launches (not inside the master VC's viewDidLoad() as most tutorials suggest). Eg,

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        ...
        let splitViewController = window!.rootViewController as! UISplitViewController
        ...
        if #available(iOS 10.0, *) {
            if let masterViewController = splitViewController.viewControllers.first as? MasterViewController {
                UNUserNotificationCenter.current().delegate = masterViewController
            }
        }
    }

This would allow iOS to call your notification delegate methods after the master VC is loaded when your app is launched cold or from the background mode.

In addition, if you need your master VC know that it was loaded because a user notification firing (and not from normal loading), you will use the NSUserDefaults to communicated this information. Hence, the AppDelegate would look as follows:

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
    ...
    let splitViewController = window!.rootViewController as! UISplitViewController
    ...
    if #available(iOS 10.0, *) {
        if let _ = launchOptions?[UIApplicationLaunchOptionsKey.localNotification] {
            UserDefaults.standard.set("yes", forKey: kMyAppLaunchedByUserNotification)
            UserDefaults.standard.synchronize()
        }
        if let masterViewController = splitViewController.viewControllers.first as? MasterViewController {
            UNUserNotificationCenter.current().delegate = masterViewController
        }
    }
}

where kMyAppLaunchedByUserNotification is a key you use to communicate with the master VC. In the viewDidAppear() for Master View Controller, you would check User Defaults to see whether it is being loaded because of notification.

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)

    if #available(iOS 10.0, *) {
        if let _ = UserDefaults.standard.object(forKey: kMyAppLaunchedByUserNotification) {
            UserDefaults.standard.removeObject(forKey: kMyAppLaunchedByUserNotification)
            UserDefaults.standard.synchronize()
            //Handle any special thing that you need to do when your app is launched from User notification as opposed to regular app launch here
            // NOTE: the notification delegate methods will be called after viewDidAppear() regardless of you doing any special thing here because you told iOS already in AppDelegate didFinishLaunchingWithOptions
        }
    }
}

I hope this helps you.