如何在iPhone上创建圆角UILabel？

import UIKit

class RoundedUILabel: UILabel {
    override func layoutSubviews() {
        super.layoutSubviews()
        layer.cornerRadius = frame.height / 2
        clipsToBounds = true
    }
}

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()

        let roundedLabel = RoundedUILabel()
        roundedLabel.text = "Hello, World!"
        roundedLabel.textAlignment = .center
        roundedLabel.frame = CGRect(x: 50, y: 50, width: 100, height: 50)
        view.addSubview(roundedLabel)
    }
}