title: UINavigationBar:appearance works but not UINavigationBar:appearanceWhenContained in
body: <p>I have a requirement to set the navigation bar to a custom color and this following code will do that:</p>
  
  <pre><code>[[UINavigationBar appearance]
              setBackgroundImage:navigationBarTileImage forBarMetrics:UIBarMetricsDefault];
  </code></pre>
  
  <p>However my application invokes the system MFMailComposeViewController and  MFMessageComposeViewController and I want the navigation bar to be the default color for those views, so I did this:</p>
  
  <pre><code>[[UINavigationBar appearanceWhenContainedIn: [MyViewControllerBase class], [MyViewController1 class], [MyViewController2 class], nil]
      setBackgroundImage:navigationBarTileImage forBarMetrics:UIBarMetricsDefault];
  </code></pre>
  
  <p>However now the navigation bar no longer has my default color.
  Why is appearanceWhenContainedIn not working?</p>