title: Unrecognized selector sent to instance in AppDelegate
body: <p>I am trying to get a method to be called every 5 seconds regardless if the app was open or was running in the background and so in my AppDelegate I thought it'd be a good idea to have a timer which calls a method every 5 seconds:</p>
  
  <pre><code>var helloWorldTimer = Timer.scheduledTimer(timeInterval: 5.0, target: self, selector: #selector(sayHello), userInfo: nil, repeats: true)
  
  @objc func sayHello()
  {
      print("hello World")
  }
  </code></pre>
  
  <p>However, I get this error:</p>
  
  <pre><code>NSInvalidArgumentException', reason: '-[_SwiftValue sayHello]: unrecognized selector sent to instance 
  </code></pre>
  
  <p>And I'm not entirely sure why because the method is referenced correctly? Does anyone understand why I'm getting this error?</p>