title: Why apple does not allow addition of one ViewController into another in Xib, though it is possible programatically
body: <p>Any reason why this is not permitted in Xib.</p>
  
  <pre><code>-(void)addLeftViewController:(UIViewController *)viewController
  {
      [self addChildViewController:viewController];
      [viewController.view setFrame:CGRectMake(0, 0, self.leftVw.frame.size.width, self.leftVw.frame.size.height)];
      [self.leftVw addSubview:viewController.view];
      [viewController didMoveToParentViewController:self];
  }
  </code></pre>