在Swift 4中使用draw-move for循环动画

import UIKit

class CustomView: UIView {
    var position: CGPoint = .zero
    var displayLink: CADisplayLink?
    
    override func draw(_ rect: CGRect) {
        // 使用Core Graphics绘制视图的外观
        let path = UIBezierPath(ovalIn: CGRect(x: position.x, y: position.y, width: 50, height: 50))
        UIColor.red.setFill()
        path.fill()
    }
    
    func startAnimation() {
        displayLink = CADisplayLink(target: self, selector: #selector(updatePosition))
        displayLink?.add(to: .main, forMode: .default)
    }
    
    @objc func updatePosition() {
        // 更新视图的位置
        position.x += 1
        position.y += 1
        
        setNeedsDisplay()
    }
}

// 在使用该自定义视图的ViewController中调用startAnimation()方法来开始动画：
let customView = CustomView(frame: CGRect(x: 0, y: 0, width: 200, height: 200))
customView.startAnimation()