title: How to assign my CustomNavigationBar to a UINavigationController?
body: <p>In order to customize the aspect of the <code>navigationBar</code> of my <code>UINavigationController</code>, I've been told to subclass the <code>UINavigationBar</code> class.</p>
  
  <p>I need to change the height of the bar, placing an image instead of the title.. etc. I can't do it just using <code>UINavigationBar</code> properties.</p>
  
  <p>Now, my issue is, how to assign to the <code>UINavigationController</code>, my <code>CustomNavigationBar</code> instance ? I can't use <code>UINavigationController.navigationBar</code> because it is read-only.</p>
  
  <p>The only way seems to load a xib, but subclassing <code>UINavigationController</code> is not reccomended by Apple, so I'm a bit confused.</p>