如何在Swift中传递C回调？考虑以下示例：

class AudioQueue {

    var desc : AudioStreamBasicDescription
    var queue : AudioQueue?

    func audioQueueHandleBuffer(ctx : UnsafeMutablePointer<()>,
                                inAQ : AudioQueue!,
                                inBuffer : AudioQueueBufferRef) {
       // do stuff
    }

    func initialize() {
        // this does not work!
        var err = AudioQueueNewOutput(&desc, audioQueueHandleBuffer,
                                      nil, nil, nil, 0, queue)

        // ...
    }
}