iOS swift - Open notifications on specific view controller

Question

When I get notifications I want to open my app to a specific screen. currently when a users taps on a notification the app just opens on the current screen open but how can I redirect to another screen instead. Please suggest any solutions?

Push notification manager:

import FirebaseMessaging

class PushNotificationManager: NSObject, MessagingDelegate, UNUserNotificationCenterDelegate {
    let userID: String
    
    init(userID: String) {
        self.userID = FriendSystem.system.CURRENT_USER_ID
        super.init()
    }
    
    func registerForPushNotifications() {
        if #available(iOS 10.0, *) {
            UNUserNotificationCenter.current().delegate = self
            
            let authOptions: UNAuthorizationOptions = [.alert, .badge, .sound]
            
            UNUserNotificationCenter.current().requestAuthorization(
                options: authOptions,
                completionHandler: {_, _ in })

            Messaging.messaging().delegate = self
        } else {
            let settings: UIUserNotificationSettings = UIUserNotificationSettings(types: [.alert, .badge, .sound], categories: nil)
            
            UIApplication.shared.registerUserNotificationSettings(settings)
        }
        
        UIApplication.shared.registerForRemoteNotifications()
        
        updateFirestorePushTokenIfNeeded()
    }
    
    func updateFirestorePushTokenIfNeeded() {
        if let token = Messaging.messaging().fcmToken {
            let usersRef = FriendSystem.system.USER_REF.document(userID)
            usersRef.setData(["fcmToken": token], merge: true)
        }
    }
    
    func messaging(_ messaging: Messaging, didReceive remoteMessage: MessagingRemoteMessage) {

    }
    
    func messaging(_ messaging: Messaging, didReceiveRegistrationToken fcmToken: String) {
        updateFirestorePushTokenIfNeeded()
    }
    
    func userNotificationCenter(_ center: UNUserNotificationCenter, didReceive response: UNNotificationResponse, withCompletionHandler completionHandler: @escaping () -> Void) {

    }
}

Push notification sender:

import Foundation

class PushNotificationSender {
    func sendPushNotification(to token: String, title: String) {
        let urlString = "https://fcm.googleapis.com/fcm/send"
        let url = NSURL(string: urlString)!
        let paramString: [String : Any] = ["to" : token,
                                           "notification" : ["title" : title],
                                           "data" : ["user" : "test_id"]
        ]
        let request = NSMutableURLRequest(url: url as URL)
        request.httpMethod = "POST"
        request.httpBody = try? JSONSerialization.data(withJSONObject:paramString, options: [.prettyPrinted])
        request.setValue("application/json", forHTTPHeaderField: "Content-Type")
        request.setValue("key=AAAA40aUkvQ:APA91bF-CnQ2x9eHtXyzBBymNvfy6YlFeN-uv8HVgSmX6Po7o8Ko3TEL7q4zwFPx8JiZnQI6pkYVIt2OlNevJr5-K-igKFB7439ssl_9lDm-6QKPLsLGfa0x3PsCCw5johTFh5UzcZe8", forHTTPHeaderField: "Authorization")
        let task =  URLSession.shared.dataTask(with: request as URLRequest)  { (data, response, error) in
            do {
                if let jsonData = data {
                    if let jsonDataDict  = try JSONSerialization.jsonObject(with: jsonData, options: JSONSerialization.ReadingOptions.allowFragments) as? [String: AnyObject] {
                        NSLog("Received data:\n\(jsonDataDict))")
                    }
                }
            } catch let err as NSError {
                print(err.debugDescription)
            }
        }
        task.resume()
    }
}

View controller:

...

let sender = PushNotificationSender()
sender.sendPushNotification(to: post_token!, title: "New notification!")

Answer 1

AppDelegate has a window property that contains all the view controllers that is being displayed.

There's a rootViewController property for the window object, which access the most bottom view controllers in the stack. The root view controller is our entry point to access view controllers from AppDelegate.

Say we want to show the ListViewController when user tap on push notification:

Just add storyboard id for the view controller in the storyboard

To jump to a particular view controller, you need to instantiate the destination view controller and push it

func jumpToViewController() {
    let storyboard = UIStoryboard(name: "Main", bundle: nil)

    // instantiate the view controller we want to show from storyboard
    // root view controller is tab bar controller (initial view controller in storyboard)
    // the selected tab is a navigation controller
    // then we push the new view controller to it
    if  let listVC = storyboard.instantiateViewController(withIdentifier: "ListViewController") as? ListViewController,
        let tabBarController = self.window?.rootViewController as? UITabBarController,
        let navController = tabBarController.selectedViewController as? UINavigationController {

            // we can modify properties of the new view controller using notification data
            // (eg: title of notification)
            listVC.title = response.notification.request.content.title
            navController.pushViewController(listVC, animated: true)
    }
}

Answer 2

You can check launchOptions to know weather the application has been launched from notification or not in didFinishLaunchingWithOptions method in appdelegate and move to your required viewcontroller accordingly.

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

     if launchOptions?[UIApplicationLaunchOptionsKey.remoteNotification] != nil {
     // Move to your required viewcontroller here
    }
}