title: How do I comment a Obj C typedef block with doxygen
body: <p>When I run doxygen on this Obj-C code, neither the signature nor the comment appears in the HTML output.  Do I need to add a tag (@typedef) or pass in settings such as ENABLE_PREPROCESSING, MACRO_EXPANSION, EXPAND_ONLY_PREDEF, PREDEFINED, and
  SHOW_FILES?  I've tried several combinations with no luck.</p>
  
  <pre><code>/**
   * This is the brief comment.  This is the detailed comment.
   *
   * @param error The error describing failure.
   */
  typedef void(^ServiceCompletion)(NSError *error);
  </code></pre>
  
  <p>Thanks in advance for any help.</p>