gistfile1.m

- (void) pushViewController:(UIViewController *)viewController animated:(BOOL)animated {
    
    newViewController.view.frame = //original frame
    [self addChildViewController:newViewController];
    
    [self transitionFromViewController:oldViewController
                      toViewController:newViewController
                              duration:(animated?0.35f:0)
                               options:0
                            animations:^{
                                newViewController.view.frame = //new frame
                            }
                            completion:^(BOOL finished) {
                                [newViewController didMoveToParentViewController:self];
                            }];
}