IPhone: How do you clip/mask a UIView?

Question

I need to mask a UIView (add rounded corners etc) but can't seem to work out how.
On the desktop i'd look at adding a mask to the CALayer but it seems the iPhone SDK excludes the functionality.
Any ideas on how I can achieve the result?
p.s. I have no control over the content being rendered in the view (user submitted images)
Cheers

Answer 1

OK, I get it now. One way I can think of is to build your view as you do now with square corners but don't add to the parent view yet. Then you can create a graphics context and setup a clipping region in the new context with round corners. Then you can draw your view into this context. Then extract an image from the context. Now you use this image to display to the user instead of the original view you created behind the scenes.
Here's code I used to convert an arbitrary view into an image. All you need to do is add the clipping code to create the rounded corners.
- (UIImage *)convertView:(UIView *)view {
UIGraphicsBeginImageContext(view.size);
CGContextRef ctx = UIGraphicsGetCurrentContext();
// Clear whole thing
CGContextClearRect(ctx, view.bounds);
// Add your code to create rounded rectangle clipping region
// Draw view into context
[view.layer renderInContext:ctx];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;