title: Could not cast value of type 'UIViewController'
body: <p>I am trying to implement BWWalkthrough in my project.  However I get an error stating</p>
  <pre><code>Unknown class _TtC20BWWalkthroughExample27BWWalkthroughViewController in Interface Builder file.
  Could not cast value of type 'UIViewController' (0x195bca580) to 'AppName.BWWalkthroughViewController' (0x10042c3a0).
  (lldb) 
  </code></pre>
  <p>It is pointing at the below code</p>
  <pre><code>let walkthrough = stb.instantiateViewControllerWithIdentifier(&quot;walk&quot;) as! BWWalkthroughViewController
  </code></pre>
  <p>I don't know why this is happening. Any help would be appreciated.</p>
  <p>Also feel free to ask for more code from my project.</p>