title: Any way to replace navigation item on UINavigationController without pushing view controller?
body: <p>I've created a view controller that's within the view controller hierarchy of a UINavigationController. This view controller contains a full-frame container view that displays the view of a child view controller.</p>
  
  <p>I'd ideally like to display the items associated with the child view controller's navigation item (i.s., <code>title</code> and <code>rightBarButtonItems</code>) instead of the navigation item of the view controller that contains the container view.</p>
  
  <p>My initial reaction is simply to set <code>viewController.navigationItem = childViewController.navigationItem</code> but <code>navigationItem</code> is read-only. My second reaction is to set the associated items themselves, e.g.:</p>
  
  <pre><code>viewController.navigationItem.title = childViewController.navigationItem.title;
  viewController.navigationItem.rightBarButtonItems = childViewController.navigationItem.rightBarButtonItems;
  </code></pre>
  
  <p>With swizzling, I'm also able to detect when the child view controller's navigation item's properties are set and update accordingly. However, if the child view controller's navigation item's properties are updated without replacement (e.g., <code>title</code> changes text color, <code>rightBarButtonItem</code> is disabled), these changes are not reflected.</p>
  
  <p>Is there any way of achieving the effect I'm looking for?</p>