title: Sharing code between original iOS App and App Extension
body: <p>Sharing class between iOS app and extension app</p>
  
  <p>I want to use a custom class in both my app and the extension app. If I just have the class in the main app folder, the extension doesn't pick up on it. I tried making a copy of it and putting it into the extension folder, but I of course get a <code>invalid redeclaration of [my class]</code> error. What's the best solution for this? It's just one class, not multiple resources.</p>