如何将渐变从顶部添加到视觉效果视图Blur - SWIFT

import UIKit
import CoreGraphics

let blurEffect = UIBlurEffect(style: .regular)
let blurView = UIVisualEffectView(effect: blurEffect)
blurView.frame = CGRect(x: 0, y: 0, width: view.frame.width, height: view.frame.height)
view.addSubview(blurView)

let gradientLayer = CAGradientLayer()
gradientLayer.frame = blurView.bounds

// 定义渐变的颜色范围和位置
let topColor = UIColor.red.cgColor
let bottomColor = UIColor.blue.cgColor
gradientLayer.colors = [topColor, bottomColor]
gradientLayer.locations = [0.0, 1.0]

blurView.layer.addSublayer(gradientLayer)