Ruby on rails 3 Rails Jquery使用remotipart gem NoMethodError上载文件：未定义的方法`name'；

我正在使用gemremotipart上传文件。 以下是我的看法：

<%= form_for @file_upload, :id => "form_feedback_attachment", :url => { :controller => "widgets", :action => "feedback_attachment_upload" }, :html => {:multipart => true} do |f| %>
   <td class="rightcol"><%= f.file_field :feedback_attachment, :id => "feedback_attachment_file" %>
   <%= f.submit "Upload" %></td>
<% end %>

但我得到了这个错误：

---

NoMethodError:nil:NilClass的未定义方法“name”。我不知道方法名在哪里，来自哪个类。任何帮助都将不胜感激。乍一看，非常感谢-您没有将：remote=>设置为true，这是表单使用ajax所必需的，因此它应该是：

<%= form_for @file_upload, :remote => true, :id => "form_feedback_attachment", :url => { :controller => "widgets", :action => "feedback_attachment_upload" }, :html => {:multipart => true} do |f| %>

还要注意，我已经删除了第一行。希望这有帮助。{

<%= form_for @file_upload, :remote => true, :id => "form_feedback_attachment", :url => { :controller => "widgets", :action => "feedback_attachment_upload" }, :html => {:multipart => true} do |f| %>

 if @file_upload
   @file_upload.feedback_attachment = params[:file_upload][:feedback_attachment]
     respond_to do |format|
      if @file_upload.save
        format.js
      end
    end
 end