Question

我有吼叫声code from apple。我收到此错误：

无法通过inout参数传递不可变值：“ CGLayerGetContext”是一个函数

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.
        }
    }
}

我该如何解决？

Answer 1

请仔细阅读来自Apple的代码，您必须创建上下文

// Calculate the adjustment
let value = (window_position + window_height - (height / 2) - (window_height / 2)) * item.options.speed;

// If the element is not fixed then adjust the algorithm
if (!item.options.fixed) {
    value += (top * -1 * item.options.speed);
}

value = Math.round(value);

并使用属性，而不是类型

private var playerItemContext = 0

和guard context == &playerItemContext else {与代码完全无关

无法通过inout参数传递不可变值：“ CGLayerGetContext”是一个函数

1 个答案: