title: trouble understanding Obj-C MVC: exit and unwindSegue
body: <p>Created a button to exit from a second ViewController to the previous ViewController. I've read in tutorials that this should be by using the "EXIT" in the view controller. (control+click+drag the button to EXIT).</p>
  
  <p>I have created an "exit" button on this second controller, and a method on the ViewController class to hook up with the control+click+drag exit segue. This method is completely empty:</p>
  
  <pre><code> - (IBAction) unwindToMainMenu:(UIStoryboardSegue *) unwindSegue
  {
  
  }
  </code></pre>
  
  <p>And yet, when I press the button it returns back to the previous ViewController as I intended, but I was expecting nothing should happen (as the method has no content).</p>
  
  <p>I assume the StoryboardSegue object passed into this method is this EXIT that I dragged the button into, but there's no code to handle that object. </p>
  
  <p>EDIT:
  Also, I am not returning anything, yet the declaration of the method says it should return an IBAction. Why is the compiler not complaining?</p>
  
  <p>Can you help me understand what am I missing?</p>