如何在 Swift 中实现 AudioServicesSystemSoundCompletionProc? [英] How do I implement AudioServicesSystemSoundCompletionProc in Swift?

问题描述

我正在尝试在 Xcode 中使用 Swift 为 AudioServicesAddSystemSoundCompletion 中的参数创建一个 AudioServicesSystemSoundCompletionProc 实例，但失败了.

I'm trying and failing to create an instance of AudioServicesSystemSoundCompletionProc for an argument in AudioServicesAddSystemSoundCompletion using Swift in Xcode.

这是我目前得到的

func completionCallback(ssID:SystemSoundID,clientData:UnsafeMutablePointer<Void>) -> Void {

}

var foo:(ssID:SystemSoundID,clientData:UnsafeMutablePointer<Void>) -> Void = completionCallback;

AudioServicesAddSystemSoundCompletion(soundID, nil, nil, foo, nil);

我在一些解释如何在 Swift 中编写等效的 C 函数指针的指南的帮助下写了这个，但这会引发这个错误:

I wrote this with the help of some guides explaining how to write equivalent C Function Pointers in Swift, but this throws this error:

'(ssID: SystemSoundID, clientData: UnsafeMutablePointer<Void>) -> Void' is not convertible to 'AudioServicesSystemSoundCompletionProc'

文档显示了 Objective-C 声明:

The documentation shows the Objective-C declaration:

typedef void (*AudioServicesSystemSoundCompletionProc) ( SystemSoundID ssID, void *clientData );

这是使用 Xcode 时显示的声明:

This is declaration shown when using Xcode:

typealias AudioServicesSystemSoundCompletionProc = CFunctionPointer<((SystemSoundID, UnsafeMutablePointer<Void>) -> Void)>

我不确定如何在 Swift 中正确实现 AudioServicesSystemSoundCompletionProc.

I'm not sure how to implement AudioServicesSystemSoundCompletionProc correctly in Swift.

推荐答案

David 的回答是正确的.但澄清一下，AudioServicesSystemSoundCompletionProc 需要在objective-c 中完成，然后桥接到swift.你可以自己编写一个实现，或者......它已经在这里为你完成:https://gist.github.com/jparishy/7b76edf8d0fcca1d63b0(大卫提到)

David's answer is correct. But just to clarify, AudioServicesSystemSoundCompletionProc needs to be done in objective-c, then bridged across to swift. You can either write an implementation yourself, or... it is already done for you here: https://gist.github.com/jparishy/7b76edf8d0fcca1d63b0 (as mentioned by David)

您需要转到该链接，下载文件 FunctionPointer.h 和 FunctionPointer.c，将其放入您的项目文件夹中，然后使用桥接头将其链接到 swift.

You need to go to that link, download the files FunctionPointer.h and FunctionPointer.c, put it in your project folder, then link it to swift using bridging header.

这样做:

• 转到您项目的构建设置，向下滚动到显示 Objective-C Bridging Header 的位置，将内容编辑为YourProject/Bridging-Header.h"(其中 YourProject 是您的项目名称)
• 在您的项目中创建一个objective-c 头文件，并将其命名为Bridging-Header.h
• 在头文件中，添加#import "FunctionPointer.h"

现在你可以在你的 swift 项目中的任何地方访问 FunctionPointer ......甜蜜

Now you can access FunctionPointer anywhere inside your swift project... sweet

回到完成处理程序，在您想要使用 AudioServicesAddSystemSoundCompletion 的代码中，执行如下操作:

Back to the compeletion handler, in your code, where you want to use AudioServicesAddSystemSoundCompletion, do something like this:

    // at the top of the class
    var functionPointer: AudioServicesCompletionFunctionPointer?

    // in the code
    var me = self
    let userData = withUnsafePointer(&me) { ptr in
        return unsafeBitCast(ptr, UnsafeMutablePointer<Void>.self)
    }
    self.functionPointer = AudioServicesCompletionFunctionPointer(systemSoundID: soundId, block: {(systemSoundID: SystemSoundID, userData: UnsafeMutablePointer<Void>) -> () in
        // sound has ended, do your stuff here
        }, userData: userData)
    AudioServicesAddSystemSoundCompletion(soundId, CFRunLoopGetMain(), kCFRunLoopDefaultMode, AudioServicesCompletionFunctionPointer.completionHandler(), userData)

您必须将 NSObject 更改为 TheClassYoureUsingThisIn 并将 soundId 更改为您的 soundId

where you'll have to change NSObject to TheClassYou'reUsingThisIn and soundId to your soundId

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