swift - Apply a shadow on a UIView that have same corner radius than view

Question

Hello i have some views with rounded corners, and I'd like to apply a shadow to this views.

SO first I round the view :

view.layer.cornerRadius = 15
view.clipsToBounds = true

then I apply the shadow :

    func dropShadow(scale: Bool = true) {
        self.layer.masksToBounds = false
        self.layer.cornerRadius = 15
        self.layer.shadowColor = UIColor.black.cgColor
        self.layer.shadowPath = UIBezierPath(roundedRect: self.bounds, cornerRadius: self.layer.cornerRadius).cgPath
        self.layer.shadowOffset = CGSize(width: 3, height: 3)
        self.layer.shadowOpacity = 0.5
        self.layer.shadowRadius = 5
    }

view.dropShadow()

I got my rounded view with a shadow but the shadow is not rounded like my view. The shadow is not rounded at all

Answer 1

You cannot cast a shadow from a view whose clipsToBounds is true. If a view's masksToBounds is true, its clipsToBounds is true; they are the same thing.

If you want a shadow to appear to come from from a view that clips, you need to use two views: one that the user can see, with rounded corners and clipsToBounds set to true, and another that the user can't see because it's behind the first one, also with rounded corners, but with clipsToBounds set to false, to cast the shadow.

class ShadowView : UIView {
    override init(frame: CGRect) {
        super.init(frame:frame)
        self.isOpaque = true
        self.backgroundColor = .black
        self.dropShadow()
    }
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    func dropShadow() {
        self.layer.masksToBounds = false
        self.layer.cornerRadius = 15
        self.layer.shadowColor = UIColor.black.cgColor
        self.layer.shadowOffset = CGSize(width: 3, height: 3)
        self.layer.shadowOpacity = 0.5
        self.layer.shadowRadius = 5
    }
}

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        let r = CGRect(x: 100, y: 100, width: 100, height: 100)
        let v = UIImageView(frame:r)
        v.image = UIImage(named:"marsSurface.jpg")
        v.clipsToBounds = true
        v.backgroundColor = .red
        v.layer.cornerRadius = 15
        self.view.addSubview(ShadowView(frame:r))
        self.view.addSubview(v)
    }
}

Note that neither view is a subview of the other, nor do they have a superview that clips, as that would clip the shadow.