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How back two UIViewController
[self.view addSubview: selectSubOpt.view];

[UIView beginAnimations:@"flipping view" context:nil];
[UIView setAnimationDuration:1];
[UIView setAnimationCurve:UIViewAnimationCurveEaseIn];
[UIView setAnimationTransition: UIViewAnimationTransitionCurlUp
                       forView:self.view.superview cache:YES];

[self.view removeFromSuperview];
[UIView commitAnimations];