how to detect collision of image views in a puzzle game

i am doing a simple jigsaw puzzle game.

for that i crop a single image into 9 pieces and display it on 9 image views.

Now i need to detect collision when one image view is comes over the half of another image view frame,

and replace image or image view each other.

how can i done can开发者_Go百科 any one please help me.

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You can use the CGRectIntersectsRect() function, it takes to CGRect's and returns YES if the rects intersect, otherwise NO.

Here is a short example:

if(CGRectIntersectsRect(image1.frame, image2.frame))
{
   UIImage *temp = [[image1 image] retain];
   [image1 setImage:image2.image];
   [image2 setIamge:[temp autorelease]];
}

(It works of course easier if you have an array to iterate through)