以某种方式生成AVPlayerItem的副本,而不是访问引用

我有一个使用AVQueuePlayer对象的简单音频播放列表。队列通过迭代包含自定义UITableViewCell对象的UITableView填充,即PlayableAudioCell。这些对象有一个AVPlayerItem属性audioTrack,我将其插入AVQueueplayer的队列中。

我想在播放和完成这些曲目时添加和删除AVPlayerItemDidPlayToEndTime观察者,以便更新我创建的音乐播放器的标签。

出于某种原因,如果队列长于2个曲目,则队列中的第三个曲目不会将观察者添加到队列中,因为应用它的函数会传递一个曲目的副本,而不是保存到PlayableAudioCell对象的曲目。

只是一些关于我的应用程序布局的解释。。。它包含一个视图,即tableViewController,允许用户选择单元格并播放曲目。我还有一个SplitViewController,它允许一个FooterView弹出并显示播放轨迹信息(标签、持续时间、轨迹滑块)。

操作顺序:

1. 用户在TableView中的单元格上按play

3. TableViewController的委托(FooterViewController)调用其委托的播放方法

4. AVPlayerItemDidPlayToEndTime观察器添加到播放的第一项中

5. 当轨迹结束时,从观测器调用选择器。在该选择器中,删除当前轨迹的观察者,并添加将AVPlayerItemDidPlayToEndTime观察者添加到下一个轨迹的代码。

与引用currentlySelectedAudioCell的audiotrack属性相反,当我访问单元格的副本或音轨的副本时,是否会弹出任何代码?

func play(cell: PlayableAudioCell){

    if let previousCell = currentlySelectedAudioCell, let prevFilename = currentlySelectedAudioCell?.chapter?.value(forKey: "Filename") as? String, let filename = cell.chapter?.value(forKey: "Filename") as? String{

        if filename != prevFilename{
            runningTime = 0
        }
    }

    updateWithObserver(cell: cell)

    //show footerview if it is hidden.
    if(footerView.superview?.isHidden)!{
        hideShowFooterView()
    }

    if(self.isPlaying)!{
        //print("Should pause cell")
        audioQueuePlayer?.pause()
        switchState(state: "Pause")

        playPauseRunTime(state: "Pause")

    }else{
        //print("Should play cell")
        audioQueuePlayer?.play()
        switchState(state: "Play")

        playPauseRunTime(state: "Play")
    }

    updateFooterView()
}

func updateWithObserver(cell: PlayableAudioCell){

    self.currentlySelectedAudioCell = cell
    delegate?.currentlySelectedAudioCell = cell

    let track = cell.audioTrack!

    NotificationCenter.default.addObserver(self, selector: #selector(FooterViewController.playerItemDidReachEnd(notification:)), name: Notification.Name.AVPlayerItemDidPlayToEndTime, object: track)

}

func playerItemDidReachEnd(notification: Notification){
    NotificationCenter.default.removeObserver(self, name: notification.name, object: audioQueuePlayer?.currentItem)

    if didAudioPlayEntirely(){
        recordAudioHistoryToFirebase(didFinish: true)
        if let currentlySelectedAudioCell = delegate?.currentlySelectedAudioCell{
            revealCheckMark(cell: currentlySelectedAudioCell)
        }
    }

    runningTime = 0

    //If there is just one more item in the queue, regardless of whether playAll() has been toggled...
    if (audioQueuePlayer?.items().count)! <= 1 {

        playPauseRunTime(state: "Pause")

        audioQueuePlayer?.removeAllItems()
        resetFooterViewUI()
        switchState(state: "Pause")
        hideShowFooterView()

        audioQueuePlayer?.rate = 0.0

        delegate?.currentlySelectedAudioCell = nil
        currentlySelectedAudioCell = nil
        delegate?.indexPathOfSelectedCell = nil
        indexPathOfSelectedCell = nil

    }else{

        if let indexPathOfSelectedCell = indexPathOfSelectedCell{

            playPauseRunTime(state: "Pause")
            playPauseRunTime(state: "Play")

            let row = indexPathOfSelectedCell.row + 1
            let newIndexPath = IndexPath(row: row, section: 0)
            self.indexPathOfSelectedCell = newIndexPath
            delegate?.indexPathOfSelectedCell = newIndexPath

            let newCell = self.tableView!.cellForRow(at: newIndexPath) as? PlayableAudioCell
            updateWithObserver(cell: newCell!)

            updateFooterView()
            self.tableView!.reloadData()

        }
    }
}