title: Init from nib, but alloc only [UIViewController]
body: <p>So I'm doing this in my code now:</p>
  
  <pre><code>UIViewController* ctrl =
       [[UIViewController alloc] // i'm alloc'ing a UIViewController...
  
         initWithNibName:@"TheNibName" // But this NIB has, within
         // interface builder, a link to "UIViewControllerDERIVATIVE".  So really,
         // `ctrl` is a UIViewControllerDERIVATIVE instance, not just
         // a UIViewController instance.
  
         bundle:nil] ;
  </code></pre>
  
  <p>The reason I'm doing this is it makes a massive convenience in writing some code that pushes modal dialogs on.. since Objective-C doesn't support &lt;template&gt;.</p>
  
  <p>My question is, <strong>is this ok??</strong>  Can I <code>[alloc]</code> a <code>UIViewController</code> only, while really what comes out of a NIB is an instance of <code>UIViewControllerDERIVATIVE</code>?  Or will it bite me in the ass later?</p>