UIView 任意圆角.swift

// iOS 11 之后的方法，来自: https: // www.appcoda.com/rounded-corners-uiview/

// layerMaxXMaxYCorner – lower right corner
// layerMaxXMinYCorner – top right corner
// layerMinXMaxYCorner – lower left corner
// layerMinXMinYCorner – top left corner

func roundCorners(cornerRadius: Double) {
    self.layer.cornerRadius = CGFloat(cornerRadius)
    self.clipsToBounds = true
    self.layer.maskedCorners = [.layerMinXMinYCorner, .layerMaxXMinYCorner]
}

// iOS 11 之前的方法
extension UIView {
   func roundCorners(corners: UIRectCorner, radius: CGFloat) {
        let path = UIBezierPath(roundedRect: bounds, byRoundingCorners: corners, cornerRadii: CGSize(width: radius, height: radius))
        let mask = CAShapeLayer()
        mask.path = path.cgPath
        layer.mask = mask
    }
}

// Use it like this
view.roundCorners(corners: [.topLeft, .topRight], radius: 20)


// 注意：当 View 改变大小的时候，mask 不会变化，需要手动改变
class View: UIView {
    override func layoutSubviews() {
        super.layoutSubviews()
        roundCorners(corners: [.topLeft, .topRight], radius: 20)
    }
}

class ViewController: UIViewController {
    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        yourView.roundCorners(corners: [.topLeft, .topRight], radius: 20)
    }
}