Swift 2 无法使用类型参数列表调用“FSEventStreamCreate”答案

【问题标题】：Swift 2 Cannot invoke 'FSEventStreamCreate' with an argument list of typeSwift 2 无法使用类型参数列表调用“FSEventStreamCreate”
【发布时间】：2015-07-02 00:43:54
【问题描述】：

使用 Swift 2 和 Xcode 7 beta 2（内部版本：7A121l）我使用 FSEventStream API 和 @convention(c) 得到这个编译错误。

任何建议都会很棒，谢谢！

internal class FileSystem {

init () {

    let allocator: CFAllocator? = kCFAllocatorDefault

    // Create FSEventStream and return valid FSEventStreamRef
    // Alias FSEventStreamCallback - CFunction

    typealias FSEventStreamCallback = @convention(c) (ConstFSEventStreamRef, UnsafeMutablePointer<Void>, UInt, UnsafeMutablePointer<Void>, UnsafePointer<FSEventStreamEventFlags>, UnsafePointer<FSEventStreamEventId>) -> Void

    let callback: FSEventStreamCallback = {
        (streamRef, clientCallBackInfo, numEvents, eventPaths, eventFlags, eventIds) -> Void in
        print ("changed")
        // handle file event
    }

    let context: UnsafeMutablePointer<FSEventStreamContext> = nil
    let pathsToWatch: CFArray = [NSHomeDirectory() + "/Dir"]
    let sinceWhen: FSEventStreamEventId = UInt64(kFSEventStreamEventIdSinceNow)
    let latency: CFTimeInterval = 1.0
    let flags: FSEventStreamCreateFlags = UInt32(kFSEventStreamCreateFlagNone)

    let eventStream = FSEventStreamCreate(
        allocator,
        callback,
        context,
        pathsToWatch,
        sinceWhen,
        latency,
        flags
    )

    FSEventStreamScheduleWithRunLoop(eventStream, CFRunLoopGetCurrent(), kCFRunLoopDefaultMode)
    FSEventStreamStart(eventStream)

}
}

【问题讨论】：

标签： ios xcode macos swift swift2

【解决方案1】：

您使用了错误的签名（UInt 不是 Int）：

typealias FSEventStreamCallback = @convention(c) (ConstFSEventStreamRef, UnsafeMutablePointer<Void>, Int, UnsafeMutablePointer<Void>, UnsafePointer<FSEventStreamEventFlags>, UnsafePointer<FSEventStreamEventId>) -> Void

这编译得很好：

init () {

    let allocator: CFAllocator? = kCFAllocatorDefault

    // Create FSEventStream and return valid FSEventStreamRef
    // Alias FSEventStreamCallback - CFunction
    typealias FSEventStreamCallback = @convention(c) (ConstFSEventStreamRef, UnsafeMutablePointer<Void>, Int, UnsafeMutablePointer<Void>, UnsafePointer<FSEventStreamEventFlags>, UnsafePointer<FSEventStreamEventId>) -> Void
    let callback: FSEventStreamCallback = {
        (streamRef, clientCallBackInfo, numEvents, eventPaths, eventFlags, eventIds) -> Void in
        print ("changed")
        // handle file event
    }


    let context: UnsafeMutablePointer<FSEventStreamContext> = nil
    let pathsToWatch: CFArray = [NSHomeDirectory() + "/Dir"]
    let sinceWhen: FSEventStreamEventId = UInt64(kFSEventStreamEventIdSinceNow)
    let latency: CFTimeInterval = 1.0
    let flags: FSEventStreamCreateFlags = UInt32(kFSEventStreamCreateFlagNone)

    let eventStream = FSEventStreamCreate(
        allocator,
        callback,
        context,
        pathsToWatch,
        sinceWhen,
        latency,
        flags
    )

    FSEventStreamScheduleWithRunLoop(eventStream, CFRunLoopGetCurrent(), kCFRunLoopDefaultMode)
    FSEventStreamStart(eventStream)

}

【讨论】：

不客气。我发现来自 Swift 编译器的一些错误消息很神秘。对我有帮助的是将组合语句分解成更小的块，手动复制本质上语法分析器和代码生成器应该在事情成熟时更好地告诉你的内容。