title: swift performSegueWithIdentifier sender value
body: <p>I am trying to understand how the sender value works in segues.</p>
  
  <p>In some places in my code both works:</p>
  
  <pre><code>performSegueWithIdentifier("mySegue", sender: self)
  
  performSegueWithIdentifier("mySegue", sender: sender)
  </code></pre>
  
  <p>But what is the difference between having self / sender?</p>