title: View controller responds to app delegate notifications in iOS 12 but not in iOS 13
body: <p>I have an app that supports iOS 12. I am adding support for iOS 13. I have a view controller that needs to perform a quick action when the app goes to the background.</p>
  
  <p>Prior to iOS 13 that is simple enough. Add a line such as:</p>
  
  <pre class="lang-swift prettyprint-override"><code>NotificationCenter.default.addObserver(self, selector: #selector(didEnterBackground), name: UIApplication.didEnterBackgroundNotification, object: nil)
  </code></pre>
  
  <p>in <code>viewDidLoad</code> or maybe an <code>init</code>.</p>
  
  <p>Then add the <code>didEnterBackground</code> method:</p>
  
  <pre class="lang-swift prettyprint-override"><code>@objc func didEnterBackground() {
      // Do my background stuff
  }
  </code></pre>
  
  <p>That's all good with iOS 12 and earlier.</p>
  
  <p>But now with scene support in iOS 13, my notification isn't being called when run with iOS 13. It still works with an iOS 12 simulator/device.</p>
  
  <p>What changes do I need to make?</p>