将物品添加到购物车首先尝试失败
我喜欢在轨道上的ruby上工作，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，首先尝试它失败并给我一个
零不能得出大的错误
但点击我的浏览器返回并在第二次尝试添加项目它工作正常，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
我的型号/ 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
Your Cart × Total
:delete, :confirm => 'Are you sure?' %>
我的型号/ line_item.rb
def total_price if product.price product.price = product.price * quantity else 0.to_d end end
完整的痕迹
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'
我有一个问题，我的第一个项目添加到我的购物车失败，但第二次添加它工作正常我只是想知道我的添加产品方法是否正确？ 在此先感谢我们更多的力量！
**编辑添加的信息**
apon跟踪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），即使我添加了默认的quaunty => 1在我的迁移文件中。
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
我通过回滚迁移20120218201140_add_quantity_to_line_item.rb来解决我的问题，并再次迁移它，它解决了我的问题，感谢帮助我们更多的力量