由于 AVPlayerItem，AVPlayer 未释放答案

【问题标题】：AVPlayer not deallocated because of AVPlayerItem由于 AVPlayerItem，AVPlayer 未释放
【发布时间】：2021-05-22 17:01:54
【问题描述】：

我在构建视频预加载时遇到了一个问题，方法是创建（持久）AVPlayerItems 并提前将它们分配给（新/临时）AVPlayers。

我看到的第一个问题是，之前分配给AVPlayer 的AVPlayerItem 如果分配给新的AVPlayer 会抛出异常。后来我把它缩小到原来的 AVPlayer 没有被释放，这就是为什么 AVPlayerItem 不能与不同的播放器一起工作“一个 AVPlayerItem 不能与多个 AVPlayer 的实例相关联”。

这是最小的可重现示例：

// AVAsset can be preloaded using `asset.loadValuesAsynchronously`.
let originalAsset = AVAsset(url: URL(string: "https://www.whatever.com")!)
// AVPlayerItem is persisted across multiple AVPlayer instances.
let playerItem = AVPlayerItem(asset: originalAsset)

// Initial preload.
var player: AVPlayer? = AVPlayer(playerItem: playerItem)
player?.replaceCurrentItem(with: nil) // Doesn't help.
player = nil // Doesn't actually deinit.


// Later at some point...
player = AVPlayer(playerItem: playerItem) // Crash here.

【问题讨论】：

标签： ios swift memory-leaks avfoundation avplayer

【解决方案1】：

解决方案是在需要将AVPlayer 分配给AVPlayer 时，通过创建一个新的AVPlayerItem 来确保AVPlayerItem 和AVPlayer 具有1:1 的关系。这是因为在AVPlayer 上设置AVPlayerItem 会在两者之间创建一个隐藏的强引用，因此持久化AVPlayerItem 会挂在AVPlayer 上，从而导致内存泄漏。

以下是一些工作示例：

// AVAsset can be preloaded using `asset.loadValuesAsynchronously`.
let originalAsset = AVAsset(url: URL(string: "https://www.whatever.com")!)
// AVPlayerItem is persisted across multiple AVPlayer instances.
// This is not necessary if you can persist the AVAsset instead (example below).
let playerItem = AVPlayerItem(asset: originalAsset)

// Initial preload.
var player = AVPlayer(playerItem: playerItem)


// Later at some point...
// Because a new `AVPlayerItem` is created, the previous one can be deallocated
// along with the `AVPlayer` instance. 
player = AVPlayer(playerItem: AVPlayerItem(asset: originalAsset))

// Some alternatives that also work:
player = AVPlayer(playerItem: AVPlayerItem(asset: playerItem.asset))
player = AVPlayer(playerItem: playerItem.copy() as? AVPlayerItem)

【讨论】：