CALayer with transparent hole in it

Question

I have a simple view (left side of the picture) and i need to create some kind of overlay (right side of the picture) to this view. This overlay should have some opacity, so

Answer 1

I took a similar approach as animal_chin, but I'm more visual, so I set most of it up in Interface Builder using outlets and auto layout.

Here is my solution in Swift

    //shadowView is a UIView of what I want to be "solid"
    var outerPath = UIBezierPath(rect: shadowView.frame)

    //croppingView is a subview of shadowView that is laid out in interface builder using auto layout
    //croppingView is hidden.
    var circlePath = UIBezierPath(ovalInRect: croppingView.frame)
    outerPath.usesEvenOddFillRule = true
    outerPath.appendPath(circlePath)

    var maskLayer = CAShapeLayer()
    maskLayer.path = outerPath.CGPath
    maskLayer.fillRule = kCAFillRuleEvenOdd
    maskLayer.fillColor = UIColor.whiteColor().CGColor

    shadowView.layer.mask = maskLayer