为什么我的 Ruby on Rails 更新购物车表单会跳过循环？

Question

我的购物车中的以下代码跳过每个商品的循环，仅输出总数，正确给出购物车的总金额。

有谁知道这是为什么？没有给出任何错误。 我正在使用 Rails 3.1.0 和 Ruby 1.9.2。

<% if notice %>
<p id="notice"><%= notice %></p>
<% end %>

<div class="cart_title">Your Cart</div>
<table>
  <% for item in @cart.line_items %>
    <% form_for item do |f| %>
      <tr>
        <td>
          <%= f.submit value: 'Update Qty' %>
          <%= f.text_field :quantity, size: 1 %>&times;
        </td>
        <td class="item_price"><%= number_to_currency(item.total_price) %></td>
      </tr>
    <% end %>
  <% end %>
  <tr class="total_line">
    <td colspan="2">Total</td>
    <td class="total_cell"><%= number_to_currency(@cart.total_price) %></td>
  </tr>
</table>

<%= button_to 'Empty cart', @cart, method: :delete,
    confirm: 'Are you sure?' %>

Development.log 显示了包含两种产品（每种产品数量 1）的购物车的此活动：

Started GET "/carts/7" for 127.0.0.1 at 2012-02-15 16:23:43 +0000
  Processing by CartsController#show as HTML
  Parameters: {"id"=>"7"}
  Cart Load (0.1ms)  SELECT "carts".* FROM "carts" WHERE "carts"."id" = ? LIMIT 1  [["id", "7"]]
  LineItem Load (0.1ms)  [1mSELECT "line_items".* FROM "line_items" WHERE "line_items"."cart_id" = 7
  Product Load (0.1ms)  SELECT "products".* FROM "products" WHERE "products"."id" = 10 LIMIT 1
  Product Load (0.1ms)  [1mSELECT "products".* FROM "products" WHERE "products"."id" = 11 LIMIT 1
Rendered carts/show.html.erb within layouts/application (41.4ms)
Completed 200 OK in 48ms (Views: 46.5ms | ActiveRecord: 0.9ms)

Answer 1

您需要对 form_for 使用 <%= ，例如：

<%= form_for item do |f| %>

这可能是循环中不显示行的原因。