嗨我正在使用ruby on rails我只是想知道我的add_product是否错误，因为当我将我的产品添加到我的购物车时，首先尝试失败并给我一个
无法识别大错误
但点击我的浏览器返回并在第二次添加项目尝试它工作正常，但没有计算我的第一次尝试添加我的产品 这是我的add_product方法
my model / cart.rb
has_many :line_items, :dependent => :destroy
def add_product(product_id)
current_item = line_items.where(:product_id => product_id).first
if current_item
current_item.quantity = current_item.quantity.to_i + 1
else
current_item = LineItem.new(:product_id=>product_id)
line_items << current_item
end
current_item
end
def total_price
Array.wrap(line_items).sum { |item| item.total_price }
end
我的购物车/ show.html.rb
<div class="cart_title" >Your Cart</div>
<table>
<% for item in @cart.line_items %>
<tr>
<td><%= item.quantity %>×</td>
<td><%= item.product.title %></td>
<td class="item_price" ><%= number_to_currency(item.total_price) %></td>
</tr>
<% 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?' %>
我的模型/ line_item.rb
def total_price
if product.price
product.price = product.price * quantity
else
0.to_d
end
end
完整追踪
app/models/line_item.rb:14:in `*'
app/models/line_item.rb:14:in `total_price'
app/views/carts/show.html.erb:7:in `block in _app_views_carts_show_html_erb___389431939__618846538'
activerecord (3.1.1) lib/active_record/associations/collection_proxy.rb:91:in `each'
activerecord (3.1.1) lib/active_record/associations/collection_proxy.rb:91:in `method_missing'
app/views/carts/show.html.erb:3:in `_app_views_carts_show_html_erb___389431939__618846538'
actionpack (3.1.1) lib/action_view/template.rb:144:in `block in render'
activesupport (3.1.1) lib/active_support/notifications.rb:55:in `instrument'
actionpack (3.1.1) lib/action_view/template.rb:142:in `render'
actionpack (3.1.1) lib/action_view/renderer/template_renderer.rb:40:in `block (2 levels) in render_template'
actionpack (3.1.1) lib/action_view/renderer/abstract_renderer.rb:33:in `block in instrument'
activesupport (3.1.1) lib/active_support/notifications.rb:53:in `block in instrument'
activesupport (3.1.1) lib/active_support/notifications/instrumenter.rb:21:in `instrument'
activesupport (3.1.1) lib/active_support/notifications.rb:53:in `instrument'
actionpack (3.1.1) lib/action_view/renderer/abstract_renderer.rb:33:in `instrument'
actionpack (3.1.1) lib/action_view/renderer/template_renderer.rb:39:in `block in render_template'
actionpack (3.1.1) lib/action_view/renderer/template_renderer.rb:47:in `render_with_layout'
actionpack (3.1.1) lib/action_view/renderer/template_renderer.rb:38:in `render_template'
actionpack (3.1.1) lib/action_view/renderer/template_renderer.rb:12:in `block in render'
actionpack (3.1.1) lib/action_view/renderer/abstract_renderer.rb:22:in `wrap_formats'
actionpack (3.1.1) lib/action_view/renderer/template_renderer.rb:9:in `render'
actionpack (3.1.1) lib/action_view/renderer/renderer.rb:36:in `render_template'
actionpack (3.1.1) lib/action_view/renderer/renderer.rb:17:in `render'
actionpack (3.1.1) lib/abstract_controller/rendering.rb:120:in `_render_template'
actionpack (3.1.1) lib/action_controller/metal/streaming.rb:250:in `_render_template'
actionpack (3.1.1) lib/abstract_controller/rendering.rb:114:in `render_to_body'
actionpack (3.1.1) lib/action_controller/metal/renderers.rb:30:in `render_to_body'
actionpack (3.1.1) lib/action_controller/metal/compatibility.rb:43:in `render_to_body'
actionpack (3.1.1) lib/abstract_controller/rendering.rb:99:in `render'
actionpack (3.1.1) lib/action_controller/metal/rendering.rb:16:in `render'
actionpack (3.1.1) lib/action_controller/metal/instrumentation.rb:40:in `block (2 levels) in render'
activesupport (3.1.1) lib/active_support/core_ext/benchmark.rb:5:in `block in ms'
/home/led/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/1.9.1/benchmark.rb:310:in `realtime'
activesupport (3.1.1) lib/active_support/core_ext/benchmark.rb:5:in `ms'
actionpack (3.1.1) lib/action_controller/metal/instrumentation.rb:40:in `block in render'
actionpack (3.1.1) lib/action_controller/metal/instrumentation.rb:78:in `cleanup_view_runtime'
activerecord (3.1.1) lib/active_record/railties/controller_runtime.rb:24:in `cleanup_view_runtime'
actionpack (3.1.1) lib/action_controller/metal/instrumentation.rb:39:in `render'
actionpack (3.1.1) lib/action_controller/metal/implicit_render.rb:10:in `default_render'
actionpack (3.1.1) lib/action_controller/metal/mime_responds.rb:268:in `block in retrieve_response_from_mimes'
actionpack (3.1.1) lib/action_controller/metal/mime_responds.rb:195:in `call'
actionpack (3.1.1) lib/action_controller/metal/mime_responds.rb:195:in `respond_to'
app/controllers/carts_controller.rb:22:in `show'
actionpack (3.1.1) lib/action_controller/metal/implicit_render.rb:4:in `send_action'
actionpack (3.1.1) lib/abstract_controller/base.rb:167:in `process_action'
actionpack (3.1.1) lib/action_controller/metal/rendering.rb:10:in `process_action'
actionpack (3.1.1) lib/abstract_controller/callbacks.rb:18:in `block in process_action'
activesupport (3.1.1) lib/active_support/callbacks.rb:416:in `_run__371692982__process_action__266900328__callbacks'
activesupport (3.1.1) lib/active_support/callbacks.rb:386:in `_run_process_action_callbacks'
activesupport (3.1.1) lib/active_support/callbacks.rb:81:in `run_callbacks'
actionpack (3.1.1) lib/abstract_controller/callbacks.rb:17:in `process_action'
actionpack (3.1.1) lib/action_controller/metal/rescue.rb:17:in `process_action'
actionpack (3.1.1) lib/action_controller/metal/instrumentation.rb:30:in `block in process_action'
activesupport (3.1.1) lib/active_support/notifications.rb:53:in `block in instrument'
activesupport (3.1.1) lib/active_support/notifications/instrumenter.rb:21:in `instrument'
activesupport (3.1.1) lib/active_support/notifications.rb:53:in `instrument'
actionpack (3.1.1) lib/action_controller/metal/instrumentation.rb:29:in `process_action'
actionpack (3.1.1) lib/action_controller/metal/params_wrapper.rb:201:in `process_action'
activerecord (3.1.1) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
actionpack (3.1.1) lib/abstract_controller/base.rb:121:in `process'
actionpack (3.1.1) lib/abstract_controller/rendering.rb:45:in `process'
actionpack (3.1.1) lib/action_controller/metal.rb:193:in `dispatch'
actionpack (3.1.1) lib/action_controller/metal/rack_delegation.rb:14:in `dispatch'
actionpack (3.1.1) lib/action_controller/metal.rb:236:in `block in action'
actionpack (3.1.1) lib/action_dispatch/routing/route_set.rb:65:in `call'
actionpack (3.1.1) lib/action_dispatch/routing/route_set.rb:65:in `dispatch'
actionpack (3.1.1) lib/action_dispatch/routing/route_set.rb:29:in `call'
rack-mount (0.8.3) lib/rack/mount/route_set.rb:152:in `block in call'
rack-mount (0.8.3) lib/rack/mount/code_generation.rb:96:in `block in recognize'
rack-mount (0.8.3) lib/rack/mount/code_generation.rb:96:in `optimized_each'
rack-mount (0.8.3) lib/rack/mount/code_generation.rb:95:in `recognize'
rack-mount (0.8.3) lib/rack/mount/route_set.rb:141:in `call'
actionpack (3.1.1) lib/action_dispatch/routing/route_set.rb:532:in `call'
actionpack (3.1.1) lib/action_dispatch/middleware/best_standards_support.rb:17:in `call'
rack (1.3.6) lib/rack/etag.rb:23:in `call'
rack (1.3.6) lib/rack/conditionalget.rb:25:in `call'
actionpack (3.1.1) lib/action_dispatch/middleware/head.rb:14:in `call'
actionpack (3.1.1) lib/action_dispatch/middleware/params_parser.rb:21:in `call'
actionpack (3.1.1) lib/action_dispatch/middleware/flash.rb:243:in `call'
rack (1.3.6) lib/rack/session/abstract/id.rb:195:in `context'
rack (1.3.6) lib/rack/session/abstract/id.rb:190:in `call'
actionpack (3.1.1) lib/action_dispatch/middleware/cookies.rb:331:in `call'
activerecord (3.1.1) lib/active_record/query_cache.rb:62:in `call'
activerecord (3.1.1) lib/active_record/connection_adapters/abstract/connection_pool.rb:477:in `call'
actionpack (3.1.1) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
activesupport (3.1.1) lib/active_support/callbacks.rb:392:in `_run_call_callbacks'
activesupport (3.1.1) lib/active_support/callbacks.rb:81:in `run_callbacks'
actionpack (3.1.1) lib/action_dispatch/middleware/callbacks.rb:28:in `call'
actionpack (3.1.1) lib/action_dispatch/middleware/reloader.rb:68:in `call'
rack (1.3.6) lib/rack/sendfile.rb:101:in `call'
actionpack (3.1.1) lib/action_dispatch/middleware/remote_ip.rb:48:in `call'
actionpack (3.1.1) lib/action_dispatch/middleware/show_exceptions.rb:47:in `call'
railties (3.1.1) lib/rails/rack/logger.rb:13:in `call'
rack (1.3.6) lib/rack/methodoverride.rb:24:in `call'
rack (1.3.6) lib/rack/runtime.rb:17:in `call'
activesupport (3.1.1) lib/active_support/cache/strategy/local_cache.rb:72:in `call'
rack (1.3.6) lib/rack/lock.rb:15:in `call'
actionpack (3.1.1) lib/action_dispatch/middleware/static.rb:53:in `call'
railties (3.1.1) lib/rails/engine.rb:456:in `call'
railties (3.1.1) lib/rails/rack/content_length.rb:16:in `call'
railties (3.1.1) lib/rails/rack/log_tailer.rb:14:in `call'
rack (1.3.6) lib/rack/handler/webrick.rb:59:in `service'
/home/led/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/1.9.1/webrick/httpserver.rb:111:in `service'
/home/led/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/1.9.1/webrick/httpserver.rb:70:in `run'
/home/led/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/1.9.1/webrick/server.rb:183:in `block in start_thread'
我在将我的第一个项目添加到我的购物车时出现问题但它失败了但是当第二次添加时它工作正常我只是想知道我的添加产品方法是否正确？ 提前感谢我们的力量！
**编辑添加的信息**
跟踪我发现的信息我发现在我第一次尝试将项目添加到购物车时，我的第一次尝试的数量不是写入数据库，1默认（例如是id 128），即使我添加了一个默认的quaunty =＆GT;我的迁移文件中有1个。
我的migragein文件 20120218201140_add_quantity_to_line_item.rb
def self.up
add_column :line_items, :quantity, :integer, :default => 1
end
已经rake db：迁移它仍然默认选项不起作用？
我的数据库
id product_id cart_id created_at updated_at quantity price
---------- ---------- ---------- -------------------------- -------------------------- ---------- ----------
127 18 37 2012-02-23 09:05:40.594604 2012-02-23 09:05:53.560155 1 321.11
128 15 37 2012-02-23 09:07:53.013923 2012-02-23 09:07:53.013923 42.95
答案 0 :(得分：0)
我解决了我的问题 回滚迁移20120218201140_add_quantity_to_line_item.rb 并再次迁移它，它解决了我的问题感谢您的帮助 对我们更有力量