AJAX调用不能在Ruby on rails上工作

我正在从“使用rails，第4版”的敏捷Web开发这本书中学习ruby。 我使用rails 3.2和ruby 1.9.2。

我尝试使用以下代码调用卡的AJAX函数

然后在控制器的“创建”动作方法中添加了line_item

  respond_to do |format| if @line_item.save # format.html { redirect_to @line_item.cart,notice: 'Line item was successfully created.' } format.html { redirect_to store_url } format.js 

然后在line_items视图中创建create.js.erb文件并添加内容

 $('#cart').html(""); 

“购物车”部分是

 
Your Cart
 
  
 
Total
 
 
 
  

“line_item”部分是

  ×    

现在，当我通过正常刷新页面来运行它时，购物车内容更新并且工作正常但是当我使用上面显示的“添加到购物车”按钮时，它会触发一个AJAX调用，似乎某种程度上控件是没有到达create.js.erb文件或“line_items”部分。 当我在开发日志中看到时，我看到了以下消息。

 Started POST "/line_items?product_id=1" for 127.0.0.1 at 2012-07-24 22:04:24 +0530 Processing by LineItemsController#create as JS Parameters: {"authenticity_token"=>"+8jnhCPyLhj26JDuaP1LRUNhVGGlOpFyJcfVXoffX+U=", "product_id"=>"1"} [1m[35mCart Load (0.2ms)[0m SELECT "carts".* FROM "carts" WHERE "carts"."id" = ? LIMIT 1 [["id", 14]] [1m[36mProduct Load (0.1ms)[0m [1mSELECT "products".* FROM "products" WHERE "products"."id" = ? LIMIT 1[0m [["id", "1"]] [1m[35mLineItem Load (0.3ms)[0m SELECT "line_items".* FROM "line_items" WHERE "line_items"."cart_id" = 14 AND "line_items"."product_id" = 1 LIMIT 1 [1m[36m (0.1ms)[0m [1mbegin transaction[0m [1m[35m (0.8ms)[0m UPDATE "line_items" SET "quantity" = 18, "updated_at" = '2012-07-24 16:34:24.620944' WHERE "line_items"."id" = 40 [1m[36m (12.1ms)[0m [1mcommit transaction[0m [1m[35mLineItem Load (0.2ms)[0m SELECT "line_items".* FROM "line_items" WHERE "line_items"."cart_id" = 14 [1m[36mProduct Load (0.2ms)[0m [1mSELECT "products".* FROM "products" WHERE "products"."id" = 1 LIMIT 1[0m Rendered line_items/_line_item.html.erb (5.3ms) Rendered carts/_cart.html.erb (7.2ms) Rendered line_items/create.js.erb (8.4ms) Completed 500 Internal Server Error in 30ms ActionView::Template::Error (undefined method `title' for nil:NilClass): 1:  2: 3: × 4:  5:  6:  7: <!--  --> app/views/line_items/_line_item.html.erb:4:in `_app_views_line_items__line_item_html_erb__4463614436040447986_70300167607120' app/views/carts/_cart.html.erb:3:in `_app_views_carts__cart_html_erb___214977825009850242_70300164957540' app/views/line_items/create.js.erb:3:in `_app_views_line_items_create_js_erb___2733752682449914066_70300166787700' app/controllers/line_items_controller.rb:52:in `create' 

请帮忙指出错误？ 谢谢

Answer 1

你得到的是没有产品的line_item。 因此，当你执行line_item.product你得到一个nil然后，当你执行nil.title时会nil.title一个错误，因此不会呈现视图。 也许你忘了在创建动作中获取（正确的）line_item？