如何在 swift 中加載像 instagram 故事這樣的視頻

Question

我正在嘗試克隆 Instagram 故事。 在 AVPlayer 中播放視頻並嘗試觀察視頻何時加載並開始播放時會出現問題，以便我可以相應地啟動和暫停計時器

這是我在集合視圖中的 controller

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

這是集合視圖單元格的代碼

    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
            
        }
    }
}