title: Do init* functions retain what is passed to them?
body: <p>I init a navigation controller with:</p>
  
  <pre><code>UINavigationController *navController = [[UINavigationController alloc] initWithRootViewController:firstViewController];
  </code></pre>
  
  <p>I wonder if the navigation controller retains firstViewController or that I need to keep it alive. When I release firstViewController, the navigation controller still works. That seems wrong.</p>
  
  <p>Clarifications?</p>