ruby-on-rails-3 – RoR：为什么我得到未定义的方法’hidden_??f

<section>
        <%= render 'shared/micropost_form_purchase' %>
        <%= render 'shared/micropost_form_sale' %>
      </section>

然后是_micropost_form_purchase.html.erb

<%= form_for(@micropost) do |f| %>
  <%= render 'shared/error_messages',object: f.object %>
  <div class="field no-indent">
    <%= f.text_area :content,placeholder: "What's something else you want to buy?" %>
    <%= f.hidden_field_tag :type,:value => "purchase" %>
  </div>
  <%= f.submit "Post",class: "btn btn-large btn-primary" %>
<% end %>

对于_micropost_form_sale.html.erb我有

<%= form_for(@micropost,:html => { :id => "sale" }) do |f| %>
  <%= render 'shared/error_messages',:value => "sale" %>
  </div>
  <%= f.submit "Post",class: "btn btn-large btn-primary" %>
<% end %>

所以我希望第一个微帖自动成为一个购买微博(我在微博数据库中有一个名为type的列,我想要描述销售或购买)和第二个我希望它成为销售微柱.我使用的是hidden_??field_tag因为我认为你不必在控制器中定义它,但我错了吗？ hidden_??field更合适吗？我该如何使用hidden_??field_tag？