title: error: /usr/include/objc/objc-class.h: No such file or directory
body: <p>I am currently using blocks in my UIButton category.  However I have come across this error which I cannot solve:</p>
  
  <blockquote>
    <p>error: /usr/include/objc/objc-class.h:
    No such file or directory</p>
  </blockquote>
  
  <p>This is the line of code that uses blocks:</p>
  
  <pre><code>FTButtonBlock block = objc_getAssociatedObject(self, "buttonBlock");
  </code></pre>