title: How to get user defined field in message file INET
body: <p>I would to send user data, so i added a field in the message file :</p>
  
  <pre><code>class MpeiMacHeader extends MacHeaderBase
  {
      MPEIMacType   type;
      uint32_t data;
  }
  </code></pre>
  
  <p>This is what the received message looks like :
  <a href="https://i.stack.imgur.com/KrcQh.png" rel="nofollow noreferrer">msg fields</a></p>
  
  <p>I didn't success to get the field <code>data</code> in my code. I tried several expressions, i could only get : <a href="https://i.stack.imgur.com/s0anK.png" rel="nofollow noreferrer">msg fields</a></p>
  
  <p>But when I try to compile with <code>msg-&gt;content</code> in my code :</p>
  
  <pre><code>no member named 'content' in 'omnetpp::cMessage'
  </code></pre>
  
  <p>How to get this field in my code ? There is a <code>getData()</code> in generated files, but i didn't find how to use it. </p>