如何防止UIView的drawRect清除以前drawRect调用绘制的路径？

override func draw(_ rect: CGRect) {
    guard let context = UIGraphicsGetCurrentContext() else { return }
    CGContextSaveGState(context)
    // 绘制路径
    CGContextRestoreGState(context)
}

let shapeLayer = CAShapeLayer()
shapeLayer.path = // 路径
shapeLayer.strokeColor = // 路径颜色
shapeLayer.fillColor = // 路径填充颜色
layer.addSublayer(shapeLayer)

let path = UIBezierPath()
// 绘制路径
let shapeLayer = CAShapeLayer()
shapeLayer.path = path.cgPath
shapeLayer.strokeColor = // 路径颜色
shapeLayer.fillColor = // 路径填充颜色
layer.addSublayer(shapeLayer)