在rails应用程序中设置下载文件的文件名

I have a controller action that allows a user to download a file with an extension of .ppt . It's not really a powerpoint binary, just an xml-ish format that powerpoint can read. the file is downloaded from the show action of a controller called ElementsController, but the show action is not actually defined in the controller, there is, however, a template file for it in app/views/elements/show.ppt.builder . I have the Mime::Type registered in config/initializers/mime_types.rb as such: I have a controller action that allows a user t