title: Having view move remaining view controller's position like Apple's location services notification
body: <p>So here is what I'm trying to do:</p>
  
  <p>I have a navigation controller <code>N</code> that manages a bunch of view controllers. Now depending on a given flag, another view controller <code>B</code> should be shown. The thing is I want <code>B</code> to always sit on top and at the bottom of the navigation controller <code>N</code>.</p>
  
  <p>Any actions that happen in the navigation controller should also be presented in that specific navigation controller and not expand to the area of <code>B</code>.</p>
  
  <p>The layout should basically look like if the navigation controller is only visible</p>
  
  <pre><code>_________
  |       |
  |       |
  |   N   |
  |       |
  |       |
  ---------
  </code></pre>
  
  <p>And this is how it is suppose to look when the flag is set to true</p>
  
  <pre><code>_________
  |       |
  |       |
  |   N   |
  |_______|
  |   B   |
  ---------
  </code></pre>
  
  <p>I'm trying to use <code>View Controller Containment</code> and was able to add <code>B</code>'s view to <code>N</code>'s hierarchy, but I can't figure out how to resize and reposition <code>N</code> and how to make sure that all new controllers that are loaded from <code>N</code> are contained in <code>N</code>'s bounds.</p>
  
  <p>I'm adding <code>B</code> as follows:</p>
  
  <pre><code>let b = BViewController()               
  presentedViewController?.addChildViewController(BViewController())
  presentedViewController?.view.addSubview(b.view)
  b.didMove(toParentViewController: presentedViewController!)
  </code></pre>
  
  <p>Where <code>presentedViewController</code> is defined as</p>
  
  <pre><code>var presentedViewController: UIViewController? {
      var viewController = AppDelegate.instance?.window?.rootViewController
      while(viewController?.presentedViewController != nil) {
          viewController = viewController?.presentedViewController
      }
  
      return viewController
  }
  </code></pre>
  
  <p>Any pointers how I can achieve this behavior?</p>
  
  <p>Basically the effect I'm trying to achieve is what Apple does with the blue rectangle when an app is currently using location services. The blue rectangle pushes all the other views down.</p>