如何在 swift 中加载像 instagram 故事这样的视频

Question

我正在尝试克隆 Instagram 故事。 在 AVPlayer 中播放视频并尝试观察视频何时加载并开始播放时会出现问题，以便我可以相应地启动和暂停计时器

这是我在集合视图中的 controller

        let url = URL(string: self.user?.stories![indexPath.row].video ?? "")
        cell.storyImage.isHidden = true
        cell.videURL = url
        cell.playVideo()

这是集合视图单元格的代码

    var player:AVPlayer!

func playVideo(){
    player = AVPlayer(url: videURL!)
    player.addObserver(self, forKeyPath: "rate", options: [.old, .new], context: nil)
    let playerLayer = AVPlayerLayer(player: player)
    playerLayer.frame = self.contentView.bounds
    self.contentView.layer.addSublayer(playerLayer)
    player.play()
}


override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
    if keyPath == "rate" {
        if player.rate > 0{
            //Trying to start timer here but it runs as soon as the cell is loaded instead of observing when the video actually starts
            
        }
    }
}