有两个 model,product 和 benefit,product has_many benefit _form.html.erb

<%= simple_form_for([:admin, @admin_product]) do |f| %>
  <%= f.error_notification %>

  <div class="form-inputs">
    <%= f.input :seo_title %>
    <%= f.input :title %>
    <%= f.input :name %>
    <%= f.input :poperty, :collection => @admin_product.poperty_enum.collect {|c| c[0]}%>
     <%= f.simple_fields_for :benefits do |benefit|%>
            <%= render :partial => 'benefit_form', :locals => { :b => benefit } %>
    <%end%>
  </div>

  <div class="form-actions">
    <%= f.button :submit %>
  </div>
<% end %>

benefit_form.html.erb

<%= b.input :title %>

。。。。。等字段

但是_form 里面不出现 benefit_form.html.erb。。。 我想嵌套多个同一个 model 表单可以怎么做呢