如何在Swift中定义MIDINotifyProc? [英] How do I define a MIDINotifyProc in Swift?

问题描述

我正在尝试使MIDI会话使用快速代码工作，并且遇到了一些委托人的问题.

I'm trying to get MIDI sessions working with swift code and am running into issues with some of the delegates.

这是 Objective-C 中的一个有效示例.

This is a working example in Objective-C.

OSStatus status = MIDIClientCreate(CFSTR("MIDI Client"), MIDIStateChangedHandler, nil, &client);

void MIDIStateChangedHandler(const MIDINotification *message, void *refCon)
{
    NSLog(@"MIDIStateChanged!");
}

这就是我正在尝试的 Swift :

var status = MIDIClientCreate("the client", notifyProc: MIDIStateChangedHandler, notifyRefCon: nil,  outClient: client) 

func MIDIStateChangedHandler(message: MIDINotification, refCon: UnsafeMutablePointer<Void>)
{
    println("MIDIStateChanged!");
}

这是我无法弄清楚的错误(我是具有多年C#经验的iOS初学者):

This is the error which I cannot figure out (I'm new to iOS with many years of C# experience):

无法将表达式的类型'(StringLiteralConvertible，notifyProc:(MIDINotification，refCon:UnsafeMutablePointer)->()，notifyRefCon:NilLiteralConvertible，outClient:@lvalue MIDIClientRef！)'转换为'StringLiteralConvertible'

cannot convert the expression's type '(StringLiteralConvertible, notifyProc: (MIDINotification, refCon: UnsafeMutablePointer) -> (), notifyRefCon: NilLiteralConvertible, outClient: @lvalue MIDIClientRef!)' to type 'StringLiteralConvertible'

var status = MIDIClientCreate("the client", notifyProc: MIDIStateChangedHandler, notifyRefCon: nil, outClient: client)

Apple没有我要使用的MIDINotifyProc或其他MIDI函数的Swift示例，并且我无法弄清楚正确的方法参数类型.

Apple does not have a Swift example for MIDINotifyProc or other MIDI functions I want to use and I can't figure out the correct method parameter type.

推荐答案

当前无法将Swift函数转换为C函数，因此仅使用Swift无法做到这一点.下面是一个示例，该示例说明了如何至少使用Objective-C做到这一点:

Currently there is no way convert Swift functions to C functions, so it is not possible to do this only with Swift. Here an example on how to do it using Objective-C as least as possible: Objective-C Wrapper for CFunctionPointer to a Swift Closure

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