问不能将不可变值作为inout参数传递：“CGLayerGetContext”是一个函数

EN

override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
    // Only handle observations for the playerItemContext
    guard context == &CGLayerGetContext else { //error here
        super.observeValue(forKeyPath: keyPath, of: object,change: change, context: context)
        return
    }

    if keyPath == #keyPath(AVPlayerItem.status) {
        let status: AVPlayerItem.Status

        // Get the status change from the change dictionary
        if let statusNumber = change?[.newKey] as? NSNumber {
            status = AVPlayerItem.Status(rawValue: statusNumber.intValue)!
        } else {
            status = .unknown
        }

        // Switch over the status
        switch status {
        case .readyToPlay: break
        // Player item is ready to play.
        case .failed: break
        // Player item failed. See error.
        case .unknown: break
            // Player item is not yet ready.
        }
    }
}