title: Get button pressed id on Swift via sender
body: <p>So I have a storyboard with 3 buttons I want to just create 1 action for all those 3 buttons and decide what to do based on their label/id...</p>
  
  <p>Is there a way to get some kind of identifier for each button?</p>
  
  <p>By the way they are images, so they don't have a title.</p>
  
  <pre><code>@IBAction func mainButton(sender: UIButton) {
      println(sender)
  }
  </code></pre>