mask layer animation

gistfile1.txt

let rect = CGRectMake(10, 10, 30, 30)
let extremePoint = CGPoint(x: CGRectGetWidth(view.bounds), y: CGRectGetHeight(view.bounds))
let circleMaskPathInitial = UIBezierPath(ovalInRect: CGRectMake(10, 10, 30, 30))
let radius = sqrt((extremePoint.x * extremePoint.x) + (extremePoint.y * extremePoint.y))
let circleMaskPathFinal = UIBezierPath(ovalInRect: CGRectInset(rect, -radius, -radius))

let maskLayer = CAShapeLayer()
maskLayer.path = circleMaskPathInitial.CGPath
view.layer.mask = maskLayer

let animation = CABasicAnimation(keyPath: "path")
animation.fromValue = circleMaskPathInitial.CGPath
animation.toValue = circleMaskPathFinal.CGPath
animation.duration = 3
animation.delegate = self
maskLayer.addAnimation(animation, forKey: "path")