title: Best way to share iphone and mac code between projects
body: <p>I realise that the view/controller stuff will be different between Mac and IPhone apps but the model code may well be similar/the same.  So whats the best way to organise a project(s) so that the model code is/can be shared?</p>
  
  <ol>
  <li>Copy/paste - just duplicate it and manually keep it in sync </li>
  <li>Have 2 xcode projects point at the same workarea - one for Mac and one for IPhone and share the code.</li>
  <li>Common library - presumably you can't do this (or can you)</li>
  </ol>
  
  <p>Thanks for any tips.</p>