animate UIImageView with flip animation

I'm a noob in objective-c and cocoa, and I would like to implement a 开发者_如何学Gosimple animation of UIImageView with flipping animation. But I'm having a hard time doing it. Below are my snippets:

UIView *containerView = [[UIView alloc] initWithFrame:CGRectMake(0,0,33,33)];
UIImageView *img1 = [[UIImageView alloc] initWithImage:[UIImage imageNamed:IMG1]];
UIImageView *img2 = [[UIImageView alloc] initWithImage:[UIImage imageNamed:IMG2]];                              
[containerView addSubview:img1];
[containerView addSubview:img2];
[self.view addSubview:containerView];

CGContextRef context = UIGraphicsGetCurrentContext();
[UIView beginAnimations:nil context:context];
[UIView setAnimationDuration:0.75];
[UIView setAnimationTransition:UIViewAnimationTransitionFlipFromLeft forView:containerView cache:YES];
[containerView exchangeSubviewAtIndex:0 withSubviewAtIndex:1];
[UIView commitAnimations];

Thanks.

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You refer to an object called view which is never declared. I think you need to change your second-to-last line to

[containerView exchangeSubviewAtIndex:0 withSubviewAtIndex:1];

See if that helps.