Simply mask a UIView with a rectangle

Question

I want to know how to simply mask the visible area of a UIView of any kind. All the answers/tutorials I\'ve read so far describe masking with an image, gradient or creating

Answer 1

Very simple example in a Swift ViewController, based on the accepted answer:

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        let redView = UIView(frame: view.bounds)
        view.addSubview(redView)

        view.backgroundColor = UIColor.green
        redView.backgroundColor = UIColor.red

        mask(redView, maskRect: CGRect(x: 50, y: 50, width: 50, height: 50))
    }

    func mask(_ viewToMask: UIView, maskRect: CGRect) {
        let maskLayer = CAShapeLayer()
        let path = CGPath(rect: maskRect, transform: nil)
        maskLayer.path = path

        // Set the mask of the view.
        viewToMask.layer.mask = maskLayer
    }
}

Output