继续包装KVO是否安全

将KVO封装在这样的延续中安全吗?我担心的是,如果 play 在调用现有的KVO回调之前再次调用 observer 将被取消绑定,并且从未调用回调,使继续挂起

var observer: NSKeyValueObservation?
var playerItem: AVPlayerItem?

func play(asset: AVURLAsset) async throws {
  playerItem = AVPlayerItem(asset: asset)

  let readyToPlay = try await withCheckedThrowingContinuation { continuation in
    observer = playerItem?.observe(\.status, changeHandler: { item, _ in
      swtich item.status:
        case .readyToPlay: continuation.resume(returning: true)
        default: continuation.resume(throwing: item.error!)
    }
  }
  ...
}