从 VTCompressionOutputCallback 中引用“self”[重复]

我目前正在尝试使用 VideoToolbox 对来自AVCaptureVideoDataOutput，但我在引用时遇到问题self从内部VTCompressionOutputCallback.

我的代码如下：

...

var sessionRef: VTCompressionSession?

let outputCallback: VTCompressionOutputCallback = { _, _, status, _, sampleBuffer in
    guard status == noErr, let sampleBuffer = sampleBuffer else {
        return
    }

    debugPrint("[INFO]: outputCallback: sampleBuffer: \(sampleBuffer)")
}

let sessionErr = VTCompressionSessionCreate(allocator: nil,
                                            width: width,
                                            height: height,
                                            codecType: kCMVideoCodecType_H264,
                                            encoderSpecification: nil,
                                            imageBufferAttributes: nil,
                                            compressedDataAllocator: nil,
                                            outputCallback: outputCallback,
                                            refcon: nil,
                                            compressionSessionOut: UnsafeMutablePointer(&sessionRef))

...

这工作正常，并且打印输出符合预期，但是一旦我尝试添加对self内VTCompressionOutputCallback，它得到一个编译器错误，指出

A C function pointer cannot be formed from a closure that captures context

我该如何使用self从回调中？

先谢谢您的帮助。

我想出了一个解决办法。

The VTCompressionSessionCreate调用有一个参数outputCallbackRefCon它被传递给VTCompressionOutputCallback.

通过将自己包裹在UnsafeMutableRawPointer like so

let unmanagedSelf = UnsafeMutableRawPointer(Unmanaged.passUnretained(self).toOpaque())

我能够将该值传递给VTCompressionSessionCreate在下面refcon范围。在回调内部，我可以使用以下命令将该值拉出来

let scopedSelf = Unmanaged<ViewController>.fromOpaque(unmanagedSelf).takeUnretainedValue()