How can I update user online status without reloading the controller?

Question

So I have made a working Chat app where the back end is Firestore (i know firebase is there.) I also have a document where users online offline status is recorder.

When the user logs in the "isOnline" node changes the value to true or "online" and when the app goes in background the value changes to "offline".

The only problem is i have to reload the viewController to make the changes take place. Is there any way I can update the users status real time

AppDelegate:-

in ApplicationDidBecomeActive

 if User.currentUser() != nil {
                updateCurrentUserInFirestore(withValues: [kISONLINE : "online"]) { (success) in
                }
            }

in ApplicationDidEnterBackground

if User.currentUser() != nil {
            updateCurrentUserInFirestore(withValues: [kISONLINE : "offline"]) { (success) in

            }
        }

Than in chatViewController setup of the navigation bar is as follows

userstatus func
     if withUser.isOnline == "online" {
                navigationController?.navigationBar.barTintColor = UIColor.flatGreen()
            }else{
               navigationController?.navigationBar.barTintColor = UIColor.flatBlue()
            }

below is the function to check the change in status

 func updateUserOnlineStatus() {

        if !isGroup! {
            var withUser = withUsers.first!


            withUserUpdateListener = reference(.User).document(withUser.isOnline).addSnapshotListener { (snapshot, error) in
                guard let snapshot = snapshot else {  return }
                if snapshot.exists {
                    print(snapshot)
                   let withUser = User(_dictionary: snapshot.data()! as NSDictionary)
                   self.setUIForSingleChat(withUser: withUser)
                }
            }

        }
    }

Answer 1

This did the trick there was some problem in the old code

func updateUserOnlineStatus() {
    print("User update online status")
    if !isGroup! {
        var withUser = withUsers.first!
        withUserUpdateListener = reference(.User).document(withUser.objectId).addSnapshotListener { (snapshot, error) in
            if error != nil {
               print("error")
            }
            print("update user status")
            let withUser = FUser(_dictionary: snapshot!.data()! as NSDictionary)
            if withUser.isOnline == "online" {
                self.navigationController?.navigationBar.barTintColor = UIColor.flatGreen()
            }else{
               self.navigationController?.navigationBar.barTintColor = UIColor.flatBlue()
            }


            }

        }

    }