Swapping rootViewController with animation

transitionWithView is intended to animate subviews of the specified container view. It is not so simple to animate changing the root view controller. I’ve spent a long time trying to do it w/o side effects. See:

Animate change of view controllers without using navigation controller stack, subviews or modal controllers?

EDIT: added excerpt from referenced answer

[UIView transitionFromView:self.window.rootViewController.view
                    toView:viewController.view
                  duration:0.65f
                   options:transition
                completion:^(BOOL finished){
                    self.window.rootViewController = viewController;
                }];