ios – Type与Alamofire不符合协议’URLRequestConvertible’

enum Router: URLRequestConvertible {
    //Error: Type 'Five100px.Router' does not conform to protocol 'URLRequestConvertible'

    static let baseURLString = "https://api.500px.com/v1"
    static let consumerKey = "MY_KEY"

    case PopularPhotos(Int)
    case PhotoInfo(Int,ImageSize)
    case Comments(Int,Int)

    var URLRequest: NSURLRequest {

        let (path,parameters) : (String,[String: AnyObject]) = {

            switch self {

            case .PopularPhotos(let page):
                let params = ["consumer_key": Router.consumerKey,"page": "\(page)","feature": "popular","rpp": "50","include_store": "store_download","include_status": "Votes"]
                return ("/phtos",params)

            case .PhotoInfo(let photoID,let ImageSize):
                var params = ["consumer_key": Router.consumerKey,"image_size": "\(ImageSize.rawValue)"]
                return ("/photos/\(photoID)",params)

            case .Comments(let photoID,let commentsPage):
                var params = ["consumer_key": Router.consumerKey,"comments": "1","comments_page": "\(commentsPage)"]
                return ("/photos/\(photoID)/comments",params)
            }
        }()

        let URL = NSURL(string: Router.baseURLString)
        let URLRequest = NSURLRequest(URL: URL!.URLByAppendingPathComponent(path))
        let encoding = Alamofire.ParameterEncoding.URL

        return encoding.encode(URLRequest,parameters: parameters).0
    }
}

我导入了Alamofire并添加了此代码,然后出现错误.我根据raywenderlich教程编写了这段代码：http://www.raywenderlich.com/85080/beginning-alamofire-tutorial,这是用Swift 1.2编写的,而我使用的是Swift 2.