title: Add a custom selector to a UIBarButtonItem
body: <p>I am an iOS newbie. I have a navigation bar button which when clicked should execute a function of my own. What is the best way to do that?</p>
  
  <pre><code>UIBarButtonItem *doneBarButtonItem=[[UIBarButtonItem alloc] init];
  doneBarButtonItem.title=@"Done";
  self.navigationItem.rightBarButtonItem = doneBarButtonItem;
  [doneBarButtonItem release];
  </code></pre>