Swift: Add Drop Shadow to a Child View

Question

I am trying to add a shadow to a child view, which is being presented (added) to my ViewController. In the past, I always added Shadows to Views like so:

slideVC.view.layer.shadowColor = UIColor(named: "Dark Background")!.cgColor
slideVC.view.layer.shadowOffset = CGSize(width: 3, height: 3)
slideVC.view.layer.shadowOpacity = 0.7
slideVC.view.layer.shadowRadius = 4.0

However, this does not work on a child view. The View has rounded corners, but no matter what I do, the corners stay round and the shadow is not added. I have experimented with clipsToBounds and MaskToBounds, without success. The Child can be dragged, that is why I cannot add a fake shadow on my ViewController beneath. Any Ideas on how I could achieve that? This is how I add my Child:

let slideVC = StartVC(customer: myCustomer)
slideVC.view.roundCorners([.topLeft, .topRight], radius: 
roundedCornersRadius.bottomSlideVC.rawValue)
slideVC.view.layer.zPosition = 15
slideVC.view.layer.shadowColor = UIColor(named: "Dark Background")!.cgColor
slideVC.view.layer.shadowOffset = CGSize(width: 3, height: 3)
slideVC.view.layer.shadowOpacity = 0.7
slideVC.view.layer.shadowRadius = 4.0
slideVC.endDelegate = self 
slideVC.shouldResizeDelegate = self
slideVC.didRemoveChildDelegate = self
add(slideVC)
        
let height = view.frame.height + 50
let width = view.frame.width
slideVC.view.frame = CGRectMake(0, self.view.frame.maxY, width, height)

Add is an extension on UIViewcontroller I use to add child controllers:

    func add(_ child: UIViewController) {
    addChild(child)
    view.addSubview(child.view)
    child.didMove(toParent: self)
}

Answer 1

You've left out a lot of information about what your code is doing, so tough to say what you might be doing wrong.

Here's a quick example of loading a view from a child view controller, rounding its corners and giving it a shadow...

First, an "add child" extension:

extension UIViewController {
    func add(_ child: UIViewController) {
        addChild(child)
        view.addSubview(child.view)
        child.didMove(toParent: self)
    }
}

next, a simple "StartVC" view controller, with a centered label (for the customer string), along with a Pan gesture to allow it to be dragged:

class StartVC: UIViewController {
    
    var customer: String = ""
    
    private var prevLocation: CGPoint = .zero
    
    init(customer: String) {
        self.customer = customer
        super.init(nibName: nil, bundle: nil)
    }
    required init?(coder: NSCoder) {
        super.init(coder: coder)
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        view.backgroundColor = .yellow
        
        let label = UILabel()
        label.font = .systemFont(ofSize: 24.0, weight: .light)
        label.textAlignment = .center
        label.numberOfLines = 0
        label.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(label)
        
        let g = view.safeAreaLayoutGuide
        NSLayoutConstraint.activate([
            label.centerYAnchor.constraint(equalTo: g.centerYAnchor),
            label.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 20.0),
            label.trailingAnchor.constraint(equalTo: g.trailingAnchor, constant: -20.0),
        ])
        
        label.text = customer
        
        let pg = UIPanGestureRecognizer(target: self, action: #selector(handlePan(_:)))
        self.view.isUserInteractionEnabled = true
        self.view.addGestureRecognizer(pg)
        
    }
    
    @objc private func handlePan(_ sender: UIPanGestureRecognizer) {
        let translation = sender.translation(in: self.view.superview)
        self.view.center = CGPoint(x: prevLocation.x + translation.x, y: prevLocation.y + translation.y)
    }
    
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        prevLocation = self.view.center
    }
    
}

and, an example view controller... we add a large-font label that will be underneath the "StartVC view" -- then it loads the child VC, gets its view, rounds the corners and sets shadow properties, and adds it centered on the view where it can then be dragged around:

class DragTestVC: UIViewController {
    
    var slideView: UIView!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // let's add a label with a bunch of text
        //  so we can see the "slide view" moving over it
        let label = UILabel()
        label.font = .systemFont(ofSize: 60.0, weight: .light)
        label.textAlignment = .center
        label.numberOfLines = 0
        label.textColor = .systemRed
        label.backgroundColor = UIColor(white: 0.95, alpha: 1.0)
        label.text = "This is just some text for the label so we can see that the \"slide view\" is being moved over other UI elements."
        
        label.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(label)
        
        let g = view.safeAreaLayoutGuide
        NSLayoutConstraint.activate([
            label.widthAnchor.constraint(equalTo: g.widthAnchor, multiplier: 0.9),
            label.centerYAnchor.constraint(equalTo: g.centerYAnchor),
            label.centerXAnchor.constraint(equalTo: g.centerXAnchor),
        ])
        
        let slideVC = StartVC(customer: "Customer\n\nRobert Smith")
        add(slideVC)
        
        slideView = slideVC.view
        
        slideView.layer.cornerRadius = 12
        slideView.layer.shadowColor = UIColor.black.cgColor
        slideView.layer.shadowOffset = CGSize(width: 3, height: 3)
        slideView.layer.shadowOpacity = 0.7
        slideView.layer.shadowRadius = 4.0

    }
    
    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)

        // let's set the "slideView" frame to
        //  60% of view width
        //  height 1.5 * its own width
        //  centered in the view
        let width = view.frame.width * 0.6
        let height = width * 1.5
        slideView.frame = .init(x: 0.0, y: 0.0, width: width, height: height)
        slideView.center = view.center
        
    }
    
}

Looks like this: