swift - 将过滤器作为参数传递给 Swift 函数？

Question

在函数中，我检索目录列表。我想让该函数接受一个过滤器参数，以便在返回目录之前过滤检索。

这是我的功能:

public func getDocumentPaths(filter: ???? = nil) -> [String] {
    do {
        var directoryUrls = try NSFileManager.defaultManager().contentsOfDirectoryAtURL(...)

        // TODO: Filter the directory contents if applicable
        if filter != nil {
            directoryUrls = directoryUrls.filter(filter)
        }

        return directoryUrls.map { $0.absoluteString }
    } catch let error as NSError {
        return [String]()
    }
}

最后，我想这样调用函数:

getDocumentPaths()
getDocumentPaths { $0.pathExtension == "mp3" }

允许这样做的过滤器参数类型是什么？

更新:基于@phimage's suggestion ，我使上述功能更像 Swift 2.0。更何况，FileKit看起来很棒!

public func getDocumentPaths() -> [String] {
    // Get the directory contents including folders
    guard let directoryUrls = try? NSFileManager.defaultManager().contentsOfDirectoryAtURL(NSURL(string:"")!, includingPropertiesForKeys: nil, options: []) else {
            // Failed so return empty list
            return [String]()
    }

    return directoryUrls.map { $0.path! }
}

Answer 1

如果你想在 NSURL 上过滤

func getDocumentPaths(filter: ((NSURL) -> Bool)? = nil) -> [String] {
    do {
        var directoryUrls = try NSFileManager.defaultManager().contentsOfDirectoryAtURL(NSURL(string:"")!, includingPropertiesForKeys: nil, options: [])   //contentsOfDirectoryAtURL(NSURL(string:"")!)

        // Filter the directory contents if applicable
        if let f = filter {
            directoryUrls = directoryUrls.filter(f)
        }

        return directoryUrls.map { $0.path }
    } catch {
        return [String]()
    }
}

如果要过滤绝对字符串

func getDocumentPaths(filter: ((String) -> Bool)? = nil) -> [String] {
    do {
        var directoryUrls = try NSFileManager.defaultManager().contentsOfDirectoryAtURL...


        var directoryStrings = directoryUrls.map { $0.path }
        // Filter the directory contents if applicable
        if let f = filter {
            directoryStrings = directoryStrings.filter(f)
        }

        return directoryStrings
    } catch {
        return [String]()
    }
}

ps:记录或重新抛出异常

ps2: 你可以使用像FileKit这样的库来轻松管理文件，有find方法