将 self 转换为 UnsafeMutablePointer<Void> 会导致 EXC_BAD_INSTRUCTION答案

【问题标题】：Casting self to UnsafeMutablePointer<Void> results in EXC_BAD_INSTRUCTION将 self 转换为 UnsafeMutablePointer<Void> 会导致 EXC_BAD_INSTRUCTION
【发布时间】：2017-04-25 07:47:59
【问题描述】：

我正在开发一个 Swift 应用程序，我在其中利用特定的 MIDI 信号并使用它。一个例子是：我想根据输入信号移动 NSSlider 的值。所以，我所做的是创建一个 MIDI 输入流（有效），我现在需要做的是获取该值并将其设置为 self.wave_mode_slider?.integerValue。

我的输入连接方法如下：

func makeInputSource() {
    var midiClient : MIDIClientRef = 0
    var inPort : MIDIPortRef = 0
    var observer = UnsafeRawPointer(Unmanaged.passUnretained(self).toOpaque())

    MIDIClientCreate("WobClient" as CFString, nil, nil, &midiClient)
    MIDIInputPortCreate(midiClient, "WobClient_InPort" as CFString, {
        (pktList: UnsafePointer<MIDIPacketList>, readProcRefCon: UnsafeMutableRawPointer?, srcConnRefCon: UnsafeMutableRawPointer?) -> Void in
        let packetList : MIDIPacketList = pktList.pointee
        var packet : MIDIPacket = packetList.packet
        let mySelf = Unmanaged<Wob>.fromOpaque(readProcRefCon!).takeUnretainedValue()

        for _ in 1...packetList.numPackets {
            let bytes = Mirror(reflecting: packet.data).children
            var params : [UInt64] = []

            var i = packet.length
            for (_, attr) in bytes.enumerated() {
                let string = String(format: "%02X ", attr.value as! UInt8)
                params.append(UInt64(strtoul(string, nil, 16)))
                i -= 1

                if (i <= 0) {
                    break
                }
            }

            mySelf.wave_mode_slider?.integerValue = ("\(params[2])" as NSString).integerValue
            packet = MIDIPacketNext(&packet).pointee
        }

    }, nil, &inPort)

    MIDIPortConnectSource(inPort, self.source, &observer)
}

如你所见，我有这样的观察者变量：

var observer = UnsafeRawPointer(Unmanaged.passUnretained(self).toOpaque())

然后我将其传递给闭包并尝试像这样使用：

let mySelf = Unmanaged<Wob>.fromOpaque(readProcRefCon!).takeUnretainedValue()

mySelf.wave_mode_slider?.integerValue = ("\(params[2])" as NSString).integerValue

但是，这会导致 EXC_BAD_INSTRUCTION 在声明 mySelf 的行上。

我也尝试使用retained 变体，但这导致了相同的EXC_BAD_INSTRUCTION。

现在，我不是一个经验丰富的 swift 开发者，尤其是在涉及到这些东西时，所以我可能错过了一些明显的东西，所以有人知道为什么会发生这种情况吗？

谢谢

编辑----按照建议，我稍微更改了代码，

MIDIPortConnectSource(inPort, self.source, &observer)

成为

MIDIPortConnectSource(inPort, self.source, observer)

这也让我将 observer 变量更改为 UnsafeMutableRawPointer

【问题讨论】：

应该是MIDIPortConnectSource(inPort, self.source, observer)，没有&——正如我在stackoverflow.com/questions/43589188/… 建议的那样：)
@MartinR 哈哈错过了！我会更新代码，因为问题仍然存在，
当然，如果你传递observer 的内容或者那个变量的地址会有所不同。
@MartinR 已编辑，:)
更改后问题仍然存在？ print(observer) 和 print(readProcRefCon!) 是否显示相同的地址？

标签： swift macos cocoa midi coremidi

【解决方案1】：

在 Swift 4 上（接收抄送）：

@objc func receiveMIDI(_ sender: UIButton) {

    let observer = UnsafeMutableRawPointer(Unmanaged.passUnretained(self).toOpaque())
    MIDIClientCreate(s, nil, nil, &midiClient);
    MIDIInputPortCreate(midiClient, p, {
    (pktList: UnsafePointer<MIDIPacketList>,
        readProcRefCon: UnsafeMutableRawPointer?, srcConnRefCon: UnsafeMutableRawPointer?) in
            // callback block
            let packetList:MIDIPacketList = pktList.pointee
            var packet:MIDIPacket = packetList.packet

            for _ in 1...packetList.numPackets{
                let bytes = Mirror(reflecting: packet.data).children
                var dumpStr = ""


                var i = packet.length
                for (_, attr) in bytes.enumerated(){
                        dumpStr += String(format:"%02d ", attr.value as! UInt8)
                        i -= 1
                        if (i <= 0)
                        {
                            break
                        }
                }
                let midi = dumpStr.split(separator: " ", maxSplits: 2, omittingEmptySubsequences: true)
                var midiIntValues = [Int(midi[0]),Int(midi[1]),Int(midi[2].trimmingCharacters(in: .whitespaces))]
                if let src = srcConnRefCon{
                    let mySelf = Unmanaged<DetailViewController>.fromOpaque(src).takeUnretainedValue()
                    if let v = midiIntValues[2]{
                       // print("control \(midiIntValues[1]) has \(v) value")
                    }

                }
                packet = MIDIPacketNext(&packet).pointee
            }
            // end callback block
        }, nil, &inputPort);

    let sourceCount = MIDIGetNumberOfSources()
    print("source count \(sourceCount)")

    for srcIndex in 0 ..< sourceCount {
        var source = MIDIGetSource(srcIndex)
        let status = MIDIPortConnectSource(inputPort,source,observer)
        if status == noErr {
            print("Connected to inputPort")
        } else {
            print("There was an error connecting the ports!")
        }
    }
}

【讨论】：