RoundedShadowView.swift

public class RoundedShadowView: UIView {

    public var cornerRadius: CGFloat = 2.0 {
        didSet {
            setNeedsLayout()
        }
    }

    public var fillColor: UIColor = .white {
        didSet {
            shadowLayer.fillColor = fillColor.cgColor
        }
    }

    public var shadowColor: UIColor = .black {
        didSet {
            shadowLayer.shadowColor = shadowColor.cgColor
        }
    }

    public var shadowOffset: CGSize = CGSize(width: 2, height: 2) {
        didSet {
            shadowLayer.shadowOffset = shadowOffset
        }
    }

    public var shadowOpacity: Float = 0.2 {
        didSet {
            shadowLayer.shadowOpacity = shadowOpacity
        }
    }

    public var shadowRadius: CGFloat = 3 {
        didSet {
            shadowLayer.shadowRadius = shadowRadius
        }
    }

    private var shadowLayer = CAShapeLayer()

    public override init(frame: CGRect) {
        super.init(frame: frame)
        setupView()
    }

    public required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        setupView()
    }

    public override func layoutSubviews() {
        super.layoutSubviews()
        configureShadowLayer()
    }

    private func setupView() {
        layer.insertSublayer(shadowLayer, at: 0)
    }

    private func configureShadowLayer() {
        shadowLayer.path = UIBezierPath(roundedRect: bounds, cornerRadius: cornerRadius).cgPath
        shadowLayer.fillColor = fillColor.cgColor

        shadowLayer.shadowColor = UIColor.black.cgColor
        shadowLayer.shadowPath = shadowLayer.path
        shadowLayer.shadowOffset = shadowOffset
        shadowLayer.shadowOpacity = shadowOpacity
        shadowLayer.shadowRadius = shadowRadius
    }
}