[ios] add Shadow on UIView using swift 3

If you need rounded shadow. Works for swift 4.2

extension UIView {

        func dropShadow() {

            var shadowLayer: CAShapeLayer!
            let cornerRadius: CGFloat = 16.0
            let fillColor: UIColor = .white

            if shadowLayer == nil {
                shadowLayer = CAShapeLayer()

                shadowLayer.path = UIBezierPath(roundedRect: bounds, cornerRadius: cornerRadius).cgPath
                shadowLayer.fillColor = fillColor.cgColor

                shadowLayer.shadowColor = UIColor.black.cgColor
                shadowLayer.shadowPath = shadowLayer.path
                shadowLayer.shadowOffset = CGSize(width: -2.0, height: 2.0)
                shadowLayer.shadowOpacity = 0.8
                shadowLayer.shadowRadius = 2

                layer.insertSublayer(shadowLayer, at: 0)
            }
        }
    }

Swift 4 rounded UIView with shadow