我希望有人能帮助我使用 Xcode 8 和 swift 3我有一个游乐场文件 Xcode 7 swift 2，它涉及 Midi 输入的 Midi 回调，在 7 中一切正常
我尝试转换为 8，它带来了有关内存的错误和一些名称更改，主要是我认为不严重的，我还使用 PlaygroundSupport 重新定义了无限循环但是，我无法克服的错误涉及MyMIDIReadProc
MIDIInputPortCreate(midiClient, "MidiTest_InPort", MyMIDIReadProc, nil, &inPort);
错误说无法将类型'（pktList： UnsafePointer， readProcRefCon： UnsafeMutablePointer， srcConnRefCon： UnsafeMutablePointer） -> Void' 的值转换为预期的参数类型'MIDIReadProc' （又名'@convention（c） （UnsafePointer， Optional>， Optional>） -> （）'）
我的理解是，它需要插入一些描述的@convention（c）包装器。我认为我走在正确的轨道上，因为您可以包装一个函数，但我对放置它的知识已经用完了。我再次希望有人能够建议
感谢您的阅读为任何糟糕的语言道歉，因为我是自学成才的
这是原始的Xcode 7代码
import Cocoa
import CoreMIDI
import XCPlayground
func getDisplayName(obj: MIDIObjectRef) -> String
{
var param: Unmanaged<CFString>?
var name: String = "Error";
let err: OSStatus = MIDIObjectGetStringProperty(obj, kMIDIPropertyDisplayName, ¶m)
if err == OSStatus(noErr)
{
name = param!.takeRetainedValue() as String
}
return name;
}
func MyMIDIReadProc(pktList: UnsafePointer<MIDIPacketList>,
readProcRefCon: UnsafeMutablePointer<Void>, srcConnRefCon: UnsafeMutablePointer<Void>) -> Void
{
let packetList:MIDIPacketList = pktList.memory;
let srcRef:MIDIEndpointRef = UnsafeMutablePointer<MIDIEndpointRef>(COpaquePointer(srcConnRefCon)).memory;
print("MIDI Received From Source: (getDisplayName(srcRef))");
var packet:MIDIPacket = packetList.packet;
for _ in 1...packetList.numPackets
{
let bytes = Mirror(reflecting: packet.data).children;
var dumpStr = "";
// bytes mirror contains all the zero values in the ridiulous packet data tuple
// so use the packet length to iterate.
var i = packet.length;
for (_, attr) in bytes.enumerate()
{
dumpStr += String(format:"$%02X ", attr.value as! UInt8);
--i;
if (i <= 0)
{
break;
}
}
print(dumpStr)
packet = MIDIPacketNext(&packet).memory;
}
}
var midiClient: MIDIClientRef = 0;
var inPort:MIDIPortRef = 0;
var src:MIDIEndpointRef = MIDIGetSource(0);
MIDIClientCreate("MidiTestClient", nil, nil, &midiClient);
MIDIInputPortCreate(midiClient, "MidiTest_InPort", MyMIDIReadProc, nil, &inPort);
MIDIPortConnectSource(inPort, src, &src);
// Keep playground running
XCPlaygroundPage.currentPage.needsIndefiniteExecution = true;
这是转换后的Xcode 8代码
var str = "Hello, playground"
import Cocoa
import CoreMIDI
import XCPlayground
import PlaygroundSupport
func getDisplayName(obj: MIDIObjectRef) -> String
{
var param: Unmanaged<CFString>?
var name: String = "Error";
let err: OSStatus = MIDIObjectGetStringProperty(obj, kMIDIPropertyDisplayName, ¶m)
if err == OSStatus(noErr)
{
name = param!.takeRetainedValue() as String
}
return name;
}
func MyMIDIReadProc(pktList: UnsafePointer<MIDIPacketList>,
readProcRefCon: UnsafeMutablePointer<Void>, srcConnRefCon: UnsafeMutablePointer<Void>) -> Void
{
let packetList:MIDIPacketList = pktList.pointee;
let srcRef:MIDIEndpointRef = UnsafeMutablePointer<MIDIEndpointRef>(OpaquePointer(srcConnRefCon)).pointee;
print("MIDI Received From Source: (getDisplayName(obj: srcRef))");
var packet:MIDIPacket = packetList.packet;
for _ in 1...packetList.numPackets
{
let bytes = Mirror(reflecting: packet.data).children;
var dumpStr = "";
var i = packet.length;
for (_, attr) in bytes.enumerated()
{
dumpStr += String(format:"$%02X ", attr.value as! UInt8);
i -= 1;
if (i <= 0)
{
break;
}
}
print(dumpStr)
packet = MIDIPacketNext(&packet).pointee;
}
}
var midiClient: MIDIClientRef = 0;
var inPort:MIDIPortRef = 0;
var src:MIDIEndpointRef = MIDIGetSource(0);
MIDIClientCreate("MidiTestClient", nil, nil, &midiClient);
MIDIInputPortCreate(midiClient, "MidiTest_InPort", MyMIDIReadProc, nil, &inPort);
MIDIPortConnectSource(inPort, src, &src);
PlaygroundPage.current.needsIndefiniteExecution = true
指针类型在 Swift 3 中发生了翻天覆地的变化。许多基于 C 的 API 的签名会相应更改。
手动执行这些更改将很痛苦。你可以让 Swift 为你工作，只需稍作修改。
尝试更改函数标头：
func MyMIDIReadProc(pktList: UnsafePointer<MIDIPacketList>,
readProcRefCon: UnsafeMutablePointer<Void>, srcConnRefCon: UnsafeMutablePointer<Void>) -> Void
{
到闭包声明：
let MyMIDIReadProc: MIDIReadProc = {pktList, readProcRefCon, srcConnRefCon in
Swift 以这种风格完美地推断参数类型。
您可能需要修复指针类型转换：
let srcRef:MIDIEndpointRef = UnsafeMutablePointer<MIDIEndpointRef>(OpaquePointer(srcConnRefCon)).pointee;
像这样：
//I'm not sure using `!` is safe here...
let srcRef: MIDIEndpointRef = UnsafeMutablePointer(srcConnRefCon!).pointee
（顺便说一下，Xcode 7 代码中的等效部分有点多余。您不需要在那里使用中间COpaquePointer。
在 Swift 3 中，指针不能为 nil，可为空的指针用 Optionals 表示。您可能需要许多其他修复才能在 Swift 3 中使用基于 C 的 API。
OOPer 正在为你指出正确的方向。这是一篇关于使用 Swift 3 Core MIDI 以及工作 github 存储库的博客文章。
假设您使用的是 CoreMIDI 1.3 或更高版本，使用 MIDIInputPortCreateWithBlock 而不是 MIDIInputPortCreate 可能会更幸运。
此方法将 Swift 块作为参数，而不需要@convention(c)函数引用，使其更适合在属于 Swift 类的方法中使用，例如：
public func midiReadBlock(ptr: UnsafePointer<MIDIPacketList>, _: UnsafeMutableRawPointer?) -> Void {
let list: MIDIPacketList = ptr.pointee
...
}
您可能还会发现这两个扩展很有用。
这个（从这里派生）允许您使用 for pkt in list 直接迭代MIDIPacketList：
extension MIDIPacketList: Sequence {
public func makeIterator() -> AnyIterator<MIDIPacket> {
var iterator: MIDIPacket?
var nextIndex: UInt32 = 0
return AnyIterator {
nextIndex += 1
if nextIndex > self.numPackets { return nil }
if iterator != nil {
iterator = withUnsafePointer(to: &iterator!) { MIDIPacketNext($0).pointee }
} else {
iterator = self.packet;
}
return iterator
}
}
}
这个向MIDIPacket中添加了一个方法，以将内容提取为[UInt8]，而不必使用真正损坏的元组语法：
extension MIDIPacket {
public var asArray: [UInt8] {
let mirror = Mirror(reflecting: self.data)
let length = Int(self.length)
var result = [UInt8]()
result.reserveCapacity(length)
for (n, child) in mirror.children.enumerated() {
if n == length {
break
}
result.append(child.value as! UInt8)
}
return result
}
}