You can do this easily by setting your view's layer mask to a CAShapeLayer
.
UIBezierPath *myClippingPath = ...
CAShapeLayer *mask = [CAShapeLayer layer];
mask.path = myClippingPath.CGPath;
myView.layer.mask = mask;
You will need to add the QuartzCore
framework to your target if you haven't already.
In Swift ...
let yourCarefullyDrawnPath = UIBezierPath( .. blah blah
let maskForYourPath = CAShapeLayer()
maskForYourPath.path = carefullyRoundedBox.CGPath
layer.mask = maskForYourPath