Transition to view controller within container view (called in performForSegue:)

gistfile1.txt

- (void)switchToViewController:(UIViewController *)viewController
{
    UIViewController *currentViewController = self.childViewControllers[0];
    [self addChildViewController:viewController];
    [self transitionFromViewController:currentViewController toViewController:viewController duration:0.2 options:UIViewAnimationOptionTransitionCrossDissolve animations:^{}
                                                 completion:^(BOOL finished) {
                                                     [currentViewController removeFromParentViewController];
                                                     [self.containerView addSubview:viewController.view];
                                                }];
}