将过滤器作为参数传递到 Swift 函数中

Question

在一个函数中，我检索一个目录列表。我想允许函数接受过滤器参数以在返回目录之前过滤检索。

这是我的函数：

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，我想像这样调用函数：

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

允许此操作的筛选器参数类型是什么？

更新：根据@phimage的建议，我使上述功能更像 Swift 2.0。更重要的是，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

如果要筛选 NSURL

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]()
    }
}

如果要按绝对字符串进行筛选

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：您可以使用FileKit等库轻松管理文件，有find方法