UITabBarController slide animation. Slide left and right when tabs are selected. Based on code from StackOverflow (linked in code)

MyTabBar.m

- (BOOL)  tabBarController:(UITabBarController *)tabBarController
shouldSelectViewController:(UIViewController *)viewController {

    // http://stackoverflow.com/questions/5161730/iphone-how-to-switch-tabs-with-an-animation
    NSUInteger controllerIndex = [self.viewControllers indexOfObject:viewController];

    if (controllerIndex == tabBarController.selectedIndex) {
        return NO;
    }

    // Get the views.
    UIView *fromView = tabBarController.selectedViewController.view;
    UIView *toView = [tabBarController.viewControllers[controllerIndex] view];

    // Get the size of the view area.
    CGRect viewSize = fromView.frame;
    BOOL scrollRight = controllerIndex > tabBarController.selectedIndex;

    // Add the to view to the tab bar view.
    [fromView.superview addSubview:toView];

    // Position it off screen.
    CGFloat screenWidth = [UIScreen mainScreen].bounds.size.width;
    toView.frame = CGRectMake((scrollRight ? screenWidth : -screenWidth), viewSize.origin.y, screenWidth, viewSize.size.height);

    [UIView animateWithDuration:0.2
                          delay:0
                        options:UIViewAnimationOptionCurveEaseInOut
                     animations:^{

                         // Animate the views on and off the screen. This will appear to slide.
                         fromView.frame = CGRectMake((scrollRight ? -screenWidth : screenWidth), viewSize.origin.y, screenWidth, viewSize.size.height);
                         toView.frame = CGRectMake(0, viewSize.origin.y, screenWidth, viewSize.size.height);
                     }

                     completion:^(BOOL finished) {
                         if (finished) {

                             // Remove the old view from the tabbar view.
                             [fromView removeFromSuperview];
                             tabBarController.selectedIndex = controllerIndex;
                         }
                     }];

    return NO;
}