iOS Changing Images using Swap effect(swap transition)

Can anyone post some sample codes in order for me to do swap effect on images?? Any generous guy can help me solve the problem?? I want to swap images using touches but i couldnt do it... Example:

-(void) touchesEnded: (NSSet *) touches withEvent: (UIEvent *) event {

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}

-(void) touchesBegan: (NSSet *) touches withEvent: (UIEvent *) event {

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}

-(void) touchesMoved: (NSSet *) touches withEvent: (UIEvent *) event {

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}