title: Why my timer doesn't want to fire at the specified interval?
body: <p>I have these two functions in my class:</p>
  
  <pre><code>func setTimer () {
      alertEndTimer = Timer.init(timeInterval: 10, target: self, selector: #selector(hideAlert), userInfo: nil, repeats: false);
      print ("NOW: \(now)") 
      print ("FIRE DATE: \(alertEndTimer!.fireDate)");
  }
  
  @IBAction func hideAlert () {
      doSomething();
  }
  </code></pre>
  
  <p>The result of the console is like this:</p>
  
  <pre><code>NOW: 2017-03-01 03:32:36 +0000
  FIRE DATE: 2017-03-01 03:32:46 +0000
  </code></pre>
  
  <p>I then put a break point on <code>doSomething();</code>. But after waiting for like 1 minute, the break point is not called at all. I also have checked whether the timer <code>isValid()</code>, and it returns true. So why doesn't my function get called?</p>