Problems with transitions between views

I try to create simple transitions between views for my app.

-(void)tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *开发者_如何学编程)viewController{
    CATransition *transition;
    transition = [CATransition animation];
    transition.type = kCAGravityLeft;
    transition.duration = 1.25;
    [[[viewController view]layer]addAnimation:transition forKey:nil];
}

I put the quartzcore.framework in my project and i call it.

My problem is that the app is launched but without the transition.

Thanks

Take a look at this topic : iPhone UIView Animation Best Practice