title: error with import <cocoa/cocoa.h>
body: <p>I added class files from another project to my new iPhone Window for the first time.   The class is a simple class that defines a polygon, and subclasses NSObject.   As part of the standard template for an Objective C class, this class definition imports Cocoa.h</p>
  
  <pre><code>#import &lt;Cocoa/Cocoa.h&gt;
  </code></pre>
  
  <p>However, just by adding this class, I'm getting an error that </p>
  
  <pre><code>Cocoa/Cocoa.h:No such file or directory.
  </code></pre>
  
  <p>I don't understand this because the exact same line occurs in another class definition (the controller) within the same project.   </p>