change UIButtonOutlet Image from AppDelegate

Question

I would like to let the user know when new content is available via the image of a button. Take snapchat for instance: the user is aware of new snaps because the left button turns red (on the mainView). I would like to do the same. I already processed the notification in the background in didReceiveRemoteNotification. Thanks to this post, I was able to awake the app in the background when a new APN arrives.

Now I would like to update the image of a button straight from applicationWillEnterForeground. This is the only way that comes to my mind as the view is already loaded when the user clicks on the app (not the banner or the notification center).

Any help would be greatly appreciated. Thank you.

Answer 1

If anybody ever comes across the same problem...

Trying to interact directly with a ViewController from the AppDelegate was obviously a terrible idea. Instead I came across this post that tells me how to know when a ViewController enters the foreground. Here is @nsgulliver answer:

override func viewDidLoad() {
    super.viewDidLoad()

     NSNotificationCenter.defaultCenter().addObserver(self, selector:"doYourStuff", name:
     UIApplicationWillEnterForegroundNotification, object: nil)
 }

 func doYourStuff(){
  // your code
 }

Then remove the observer:

deinit {
        NSNotificationCenter.defaultCenter().removeObserver(self)
       }