无法将类型为“Mappable”的类分配给AlamoFire响应

Question

所以我正在使用Alamofire进行提取，并且根据索引（请参阅switch currentIndex）我想获得一个不同的URL（有效）和一个Class（不起作用）。

类文件夹和文章都声明如下：class Folders : Mappable和class Article : Mappable

    var responseMapping:Mappable?
    var URL:String = ""
    switch currentIndex {
    case 0:
        URL = "searchFolderURL".localized + searchString
        responseMapping = Folders
    case 1:
        URL = "searchArticleURL".localized + searchString
        responseMapping = Article
    default:
        print("Something went horribly wrong")
        guard URL != "" else {
            return
        }
    }
    print(URL)

    Alamofire.request(.GET, URL).responseObject { (response: Response<responseMapping, NSError>) in
        if response.result.isSuccess {

当我尝试以下代码时，它会返回下一个错误：'responseMapping' is not a type和Cannot assign value of type 'Article.Type' to type 'Mappable?'

我在这里缺少什么？