ios containerViewController

 - (void)replaceViewController:(UIViewController *)existingViewController withViewController:(UIViewController *)newViewController inContainerView:(UIView *)containerView completion:(void (^)(void))completion
 {
     // Add initial view controller
     if (!existingViewController && newViewController) {
         [newViewController willMoveToParentViewController:self];
         [newViewController beginAppearanceTransition:YES animated:NO];
         [self addChildViewController:newViewController];
         newViewController.view.frame = containerView.bounds;
         [containerView addSubview:newViewController.view];
         [newViewController didMoveToParentViewController:self];
         [newViewController endAppearanceTransition];
         if (completion) completion();
     }
     // Remove existing view controller
     else if (existingViewController && !newViewController) {
         [existingViewController willMoveToParentViewController:nil];
         [existingViewController beginAppearanceTransition:NO animated:NO];
         [existingViewController.view removeFromSuperview];
         [existingViewController removeFromParentViewController];
         [existingViewController didMoveToParentViewController:nil];
         [existingViewController endAppearanceTransition];
         if (completion) completion();
     }
     // Replace existing view controller with new view controller
     else if ((existingViewController != newViewController) && newViewController) {
         [newViewController willMoveToParentViewController:self];
         [existingViewController willMoveToParentViewController:nil];
         [existingViewController beginAppearanceTransition:NO animated:NO];
         [existingViewController.view removeFromSuperview];
         [existingViewController removeFromParentViewController];
         [existingViewController didMoveToParentViewController:nil];
         [existingViewController endAppearanceTransition];
         [newViewController beginAppearanceTransition:YES animated:NO];
         newViewController.view.frame = containerView.bounds;
         [self addChildViewController:newViewController];
         [containerView addSubview:newViewController.view];
         [newViewController didMoveToParentViewController:self];
         [newViewController endAppearanceTransition];
         if (completion) completion();
     }
 }