title: Finding out where I am in uinavigationcontroller hierarchy, or if view has been pushed?
body: <p>I've got a view that sometimes appears as a pushed view of uinavigationcontroller, and sometime just as the initial view of a tab-bar item.</p>
  
  <p>There's a 'Save' button on the interface which I want to make the view pop back to previous view when it's been pushed onto screen, and do nothing when it's being displayed as part of a tab bar selected screen.</p>
  
  <p>In pseudo-code, I guess what I want to do is:</p>
  
  <pre><code>if view-has-been-pushed, then pop back, else do nothing
  </code></pre>
  
  <p>How can I tell if the view has been pushed?</p>