title: How do I create a UITabBarController with a custom UITabBar class without using IB?
body: <p>I can create a <code>UINavigationController</code> with custom bar classes by using <code>initWithNavigationBarClass:toolbarClass:</code>.  There doesn't seem to be an equivalent for <code>UITabBarController</code>, so how do I get it to use a custom <code>UITabBar</code> class?</p>
  
  <p>Every solution I've seen so far is unsuitable because either</p>
  
  <ol>
  <li>It uses IB</li>
  <li>It adds a second tab bar to the <code>UITabBarController</code> instead of changing its existing one, or</li>
  <li>It throws <code>UITabBarController</code> away and makes a new controller class.</li>
  </ol>
  
  <p>I want a real <code>UITabBarController</code> created in code using a custom class for its tab bar.  How do I achieve this?</p>