title: Changing objective C file extension from .m to .mm causes errors
body: <p>Originally I had the file containing the warning below in LoginViewController.m, which I ignored. And the code works fine.</p>
  
  <pre><code>warning: sending 'LoginViewController *' to parameter of incompatible type 'id&lt;NSStreamDelegate&gt;'
  </code></pre>
  
  <p>But now I changed the file extention to .mm (LoginViewController.mm). Now I can no longer build the project, because of this error.</p>
  
  <pre><code>Cannot initialize a parameter of type 'id&lt;NSStreamDelegate&gt;' with an lvalue of type 'LoginViewController *'
  </code></pre>
  
  <p>Whats wrong?</p>