Programmatically return to first controller on event of THAT first controller

Question

In my Swift project, ViewController #1 has a route of destinations listed in a table. User is driving along and we keep track of where user is using the built-in CLLocation stuff. But user has now navigated away from ViewController #1 to some other portion of the app and is now in ViewController #2. A certain event that I track in ViewController #1 fires (in my example; the user has reached the next destination on his list). I need the app to immediately segue back to ViewController #1 right when that event fires. How can it be sensed when user is in ViewController #2?

Answer 1

NSNotificationCenter and an Unwind Segue seems to be the way to go, this way this functionality can be reused, all you would need to do is register for a given notification on the relevant view controllers.

Something along the lines of:

class ViewControllerOne: UIViewController {

    let CallForUnwindSegue = "com.yourIdentifier.unwindToVCOne"

    //- your event happens
    SomethingHappened {
        NSNotificationCenter.defaultCenter().postNotification(CallForUnwindSegue, object: nil)
    }
}


class ViewControllerTwo: UIViewController {

    let CallForUnwindSegue = "com.yourIdentifier.unwindToVCOne"

    override func viewDidLoad() {
        super.viewDidLoad()

    //- Subscribe for notifications
        NSNotificationCenter.defaultCenter().addObserver(self, #selector(self.doSomething), name: CallForUnwindSegue)
    }

    //- Unsubscribe for notifications
    override func deinit {
        NSNotificationCenter.defaultCenter().removeObserver(self)
    }

    func doSomething(notification: NSNotification) {
        //Handle your event here.
    }
}

There's a good unwind segue article here