title: C++ class formats - Qt creator 5.2.1
body: <p>I'm a little new to C++, mostly deal with some embedded C development, but I don't do much with classes. I saw this in a Qt example header file:</p>
  
  <pre><code>class QUdpSocket;
  </code></pre>
  
  <p>Is this a class constructor? I know QUdpSocket is a class of it's own, in a header file, and part of the QAbstractSocket Class, but I've never encountered it this way. It confounds me a bit, can someone shed a little light on this? As I said, new to C++ and learning...</p>
  
  <p>Thanks :-)</p>