如何更改AVPlayer视频的速率

import AVFoundation
import UIKit

class ViewController: UIViewController {
    var player: AVPlayer?
    var playerLayer: AVPlayerLayer?

    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 创建一个播放器项
        guard let url = URL(string: "https://example.com/video.mp4") else { return }
        let playerItem = AVPlayerItem(url: url)
        
        // 初始化播放器
        player = AVPlayer(playerItem: playerItem)
        playerLayer = AVPlayerLayer(player: player)
        playerLayer?.frame = view.bounds
        view.layer.addSublayer(playerLayer!)
        
        // 开始播放
        player?.play()
        
        // 更改播放速率
        changePlaybackRate(to: 1.5) // 设置为1.5倍速
    }
    
    func changePlaybackRate(to rate: Float) {
        player?.rate = rate
    }
}