如何在iPhone的xcode 4中制作customUI对象

import UIKit

class CustomUI: UIView {
    override init(frame: CGRect) {
        super.init(frame: frame)
        backgroundColor = .red
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func draw(_ rect: CGRect) {
        super.draw(rect)
        let context = UIGraphicsGetCurrentContext()
        context?.setStrokeColor(UIColor.black.cgColor)
        context?.setLineWidth(2)
        context?.move(to: CGPoint(x: 10, y: 10))
        context?.addLine(to: CGPoint(x: rect.width - 10, y: rect.height - 10))
        context?.strokePath()
    }
}

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        let customUI = CustomUI(frame: CGRect(x: 50, y: 50, width: 100, height: 100))
        view.addSubview(customUI)
    }
}