iphone - UIBezierPath Subtract Path

Question

By using [UIBezierPath bezierPathWithRoundedRect:byRoundingCorners:cornerRadii:], I am able to create a rounded view, such as this:

How could I subtract another path from this one (or some other way), to create a path like this:

Is there any way I can do something like this? Pseudocode:

UIBezierPath *bigMaskPath = [UIBezierPath bezierPathWithRoundedRect:bigView.bounds 
                                 byRoundingCorners:(UIRectCornerTopLeft|UIRectCornerTopRight)
                                       cornerRadii:CGSizeMake(18, 18)];
UIBezierPath *smallMaskPath = [UIBezierPath bezierPathWithRoundedRect:smalLView.bounds 
                                     byRoundingCorners:(UIRectCornerTopLeft|UIRectCornerTopRight)
                                           cornerRadii:CGSizeMake(18, 18)];

UIBezierPath *finalPath = [UIBezierPath pathBySubtractingPath:smallMaskPath fromPath:bigMaskPath];

Answer 1

Actually there is a much simpler way for most cases, example in Swift:

path.append(cutout.reversing())

This works because the default fill rule is the non-zero winding rule.