将 ios 的“播放器”框架更新为 swift 3答案

【问题标题】：Update "Player" framework for ios to swift 3将 ios 的“播放器”框架更新为 swift 3
【发布时间】：2016-09-08 21:53:20
【问题描述】：

我正在开发一个使用 https://github.com/piemonte 的“播放器”框架的应用程序自从我更新到 swift 3 后，我收到关于一个特定功能的错误。我不确定如何解决它，因为我还不是 swift 3 的专业人士。有什么帮助吗？ :D

代码（swift 2.3）（请帮我更新到swift 3）

private var PlayerObserverContext = 0
private var PlayerItemObserverContext = 0
private var PlayerLayerObserverContext = 0

    override open func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {

    switch (keyPath, context) {
    case (.some(PlayerRateKey), PlayerObserverContext):
        true
    case (.some(PlayerStatusKey), PlayerItemObserverContext):
        true
    case (.some(PlayerKeepUp), PlayerItemObserverContext):
        if let item = self.playerItem {
            self.bufferingState = .ready
            self.delegate?.playerBufferingStateDidChange(self)

            if item.isPlaybackLikelyToKeepUp && self.playbackState == .playing {
                self.playFromCurrentTime()
            }
        }

        let status = (change?[NSKeyValueChangeKey.newKey] as! NSNumber).intValue as AVPlayerStatus.RawValue

        switch (status) {
        case AVPlayerStatus.readyToPlay.rawValue:
            self.playerView.playerLayer.player = self.player
            self.playerView.playerLayer.isHidden = false
        case AVPlayerStatus.failed.rawValue:
            self.playbackState = PlaybackState.failed
            self.delegate?.playerPlaybackStateDidChange(self)
        default:
            true
        }
    case (.some(PlayerEmptyBufferKey), PlayerItemObserverContext):
        if let item = self.playerItem {
            if item.isPlaybackBufferEmpty {
                self.bufferingState = .delayed
                self.delegate?.playerBufferingStateDidChange(self)
            }
        }

        let status = (change?[NSKeyValueChangeKey.newKey] as! NSNumber).intValue as AVPlayerStatus.RawValue

        switch (status) {
        case AVPlayerStatus.readyToPlay.rawValue:
            self.playerView.playerLayer.player = self.player
            self.playerView.playerLayer.isHidden = false
        case AVPlayerStatus.failed.rawValue:
            self.playbackState = PlaybackState.failed
            self.delegate?.playerPlaybackStateDidChange(self)
        default:
            true
        }
    case (.some(PlayerReadyForDisplay), PlayerLayerObserverContext):
        if self.playerView.playerLayer.isReadyForDisplay {
            self.delegate?.playerReady(self)
        }
    default:
        super.observeValue(forKeyPath: keyPath, of: object, change: change, context: context)

    }

}

【问题讨论】：

标签： ios swift avfoundation swift3 xcode8

【解决方案1】：

我会用 guard 语句打开 context 并像这样匹配：

override open func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
    guard let context = context else {
        return
    }

    switch (keyPath, context) {
    case (.some(PlayerRateKey), &PlayerObserverContext):
        break
    case (.some(PlayerStatusKey), &PlayerItemObserverContext):
        break
    case (.some(PlayerKeepUpKey), &PlayerItemObserverContext):
        break
    // etc
   }
}

应该编译并运行。

我也会把trues 变成breaks。我不确定trues 的用途。

【讨论】：