title: Hidden features of Objective-C
body: <p>Objective-C is getting wider use due to its use by Apple for Mac OS X and iPhone development. What are some of your favourite "hidden" features of the Objective-C language?</p>
  
  <ul>
  <li>One feature per answer.</li>
  <li>Give an example and short description of the feature, not just a link to documentation.</li>
  <li>Label the feature using a title as the first line.</li>
  </ul>