# adding items to cart first attemp fail **URL:** \ **Category:** rubyonrails-talk\ **Created:** [February 21, 2012, 10:32am UTC](https://discuss.rubyonrails.org/t/adding-items-to-cart-first-attemp-fail/62921 "2012-02-21T10:32:39Z")\ **Posts on this page:** 1\ **Page:** 1
**Author:** ![11155](https://avatars.discourse-cdn.com/v4/letter/1/d26b3c/32.png) [@11155](https://discuss.rubyonrails.org/u/11155)\ **Post date:** [February 21, 2012, 10:32am UTC](https://discuss.rubyonrails.org/t/adding-items-to-cart-first-attemp-fail/62921/1 "2012-02-21T10:32:39Z")
hi im workiing on ruby on rails im just wondering if my add\_product is wrong because when i add my product in to my cart at first attemp it fail and give me a nil cannot concien bigdecimal error but clicking return from my browser and add item at the second attemp it worked fine and but didnt count my first attemp of adding my product this is my add\_product method 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 my cart/show.html.rb: \
Your Cart\     \         \<% for item in @cart.line\_items %\>     \         \\<%= item.quantity %\>×\         \\<%= item.product.title %\>\     \\<%= number\_to\_currency(item.total\_price) %\>\     \     \<% end %\>         \         \Total\         \\<%= number\_to\_currency(@cart.total\_price) %\>\     \     \         \<%= button\_to 'Empty cart', @cart, :method =\> :delete,         :confirm =\> 'Are you sure?' %\> my model/line\_item.rb def total\_price      if product.price        product.price = product.price \* quantity      else         0.to\_d      end    end full trace: 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' im having a problem in adding my first item in to my cart it fails but when adding second time it worked fine im just wondering if my adding product method is right? thanks in advance more power to us!