如何将渐变应用于从路径创建的SKShapeNode

import SpriteKit

// 创建一个路径
let path = CGMutablePath()
path.move(to: CGPoint(x: 0, y: 0))
path.addLine(to: CGPoint(x: 100, y: 0))
path.addLine(to: CGPoint(x: 100, y: 100))
path.addLine(to: CGPoint(x: 0, y: 100))
path.closeSubpath()

// 创建一个SKShapeNode对象
let shapeNode = SKShapeNode(path: path)

// 创建一个CAGradientLayer对象
let gradientLayer = CAGradientLayer()
gradientLayer.frame = shapeNode.frame

// 定义渐变的起始点和结束点
gradientLayer.startPoint = CGPoint(x: 0, y: 0)
gradientLayer.endPoint = CGPoint(x: 1, y: 1)

// 定义渐变的颜色
gradientLayer.colors = [UIColor.red.cgColor, UIColor.blue.cgColor]

// 将CAGradientLayer对象添加到SKShapeNode的layer属性中
shapeNode.layer.addSublayer(gradientLayer)

// 在场景中添加SKShapeNode对象
let scene = SKScene(size: CGSize(width: 200, height: 200))
scene.addChild(shapeNode)