Ruby on rails 调用destroy方法会给出错误-未定义的方法`name'；对于nil:NilClass-Rails 4

尝试删除产品时，我遇到此错误

NoMethodError in ProductsController#destroy
undefined method `name' for nil:NilClass

控制器：

class ProductsController < ApplicationController
 before_action :set_product, only: [:show, :edit, :update, :destroy]

 def destroy
  @product.destroy <-------error highlights on this line
  respond_to do |format|
   format.html { redirect_to some_path }
   format.json { head :no_content }
  end
 end

 private

 def set_product
  @product = Product.find(params[:id])
 end

class Product < ActiveRecord::Base

 belongs_to :category
 belongs_to :sub_category

 has_one :item , :dependent => :delete
 has_many :carts, :dependent => :delete_all
 has_many :assets , :dependent => :delete_all

end

完整跟踪：

activerecord (4.0.1) lib/active_record/associations/has_many_association.rb:81:in `cached_counter_attribute_name'
activerecord (4.0.1) lib/active_record/associations/has_many_association.rb:104:in `inverse_updates_counter_cache?'
activerecord (4.0.1) lib/active_record/associations/has_many_association.rb:114:in `delete_records'
activerecord (4.0.1) lib/active_record/associations/collection_association.rb:493:in `remove_records'
activerecord (4.0.1) lib/active_record/associations/collection_association.rb:486:in `block in delete_or_destroy'
activerecord (4.0.1) lib/active_record/associations/collection_association.rb:152:in `block in transaction'
activerecord (4.0.1) lib/active_record/connection_adapters/abstract/database_statements.rb:200:in `transaction'
activerecord (4.0.1) lib/active_record/transactions.rb:209:in `transaction'
activerecord (4.0.1) lib/active_record/associations/collection_association.rb:151:in `transaction'
activerecord (4.0.1) lib/active_record/associations/collection_association.rb:486:in `delete_or_destroy'
activerecord (4.0.1) lib/active_record/associations/collection_association.rb:247:in `destroy'
activerecord (4.0.1)  lib/active_record/associations/collection_association.rb:170:in `destroy_all'
activerecord (4.0.1) lib/active_record/associations/has_many_association.rb:26:in `handle_dependency'
 activerecord (4.0.1) lib/active_record/associations/builder/association.rb:97:in `has_many_dependent_for_assets'
 activesupport (4.0.1) lib/active_support/callbacks.rb:397:in `_run__3353912714138952721__destroy__callbacks'
 activesupport (4.0.1) lib/active_support/callbacks.rb:80:in `run_callbacks'
 activerecord (4.0.1) lib/active_record/callbacks.rb:292:in `destroy'
 activerecord (4.0.1) lib/active_record/transactions.rb:265:in `block in destroy'
activerecord (4.0.1) lib/active_record/transactions.rb:326:in `block in with_transaction_returning_status'
activerecord (4.0.1) lib/active_record/connection_adapters/abstract/database_statements.rb:202:in `block in transaction'
activerecord (4.0.1) lib/active_record/connection_adapters/abstract/database_statements.rb:210:in `within_new_transaction'
activerecord (4.0.1) lib/active_record/connection_adapters/abstract/database_statements.rb:202:in `transaction'
activerecord (4.0.1) lib/active_record/transactions.rb:209:in `transaction'
activerecord (4.0.1) lib/active_record/transactions.rb:323:in `with_transaction_returning_status'
activerecord (4.0.1) lib/active_record/transactions.rb:265:in `destroy'
app/controllers/products_controller.rb:225:in `destroy'
    actionpack (4.0.1) lib/action_controller/metal/implicit_render.rb:4:in `send_action'
    actionpack (4.0.1) lib/abstract_controller/base.rb:189:in `process_action'
    actionpack (4.0.1) lib/action_controller/metal/rendering.rb:10:in `process_action'
    actionpack (4.0.1) lib/abstract_controller/callbacks.rb:18:in `block in process_action'
    activesupport (4.0.1) lib/active_support/callbacks.rb:493:in `_run__3348285909198205465__process_action__callbacks'
    activesupport (4.0.1) lib/active_support/callbacks.rb:80:in `run_callbacks'
    actionpack (4.0.1) lib/abstract_controller/callbacks.rb:17:in `process_action'
    actionpack (4.0.1) lib/action_controller/metal/rescue.rb:29:in `process_action'
    actionpack (4.0.1) lib/action_controller/metal/instrumentation.rb:31:in `block in process_action'
    activesupport (4.0.1) lib/active_support/notifications.rb:159:in `block in instrument'
    activesupport (4.0.1) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
    activesupport (4.0.1) lib/active_support/notifications.rb:159:in `instrument'
    actionpack (4.0.1) lib/action_controller/metal/instrumentation.rb:30:in `process_action'
    actionpack (4.0.1) lib/action_controller/metal/params_wrapper.rb:245:in `process_action'
    activerecord (4.0.1) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
    actionpack (4.0.1) lib/abstract_controller/base.rb:136:in `process'
 actionpack (4.0.1) lib/abstract_controller/rendering.rb:44:in `process'
actionpack (4.0.1) lib/action_controller/metal.rb:195:in `dispatch'
actionpack (4.0.1) lib/action_controller/metal/rack_delegation.rb:13:in `dispatch'
actionpack (4.0.1) lib/action_controller/metal.rb:231:in `block in action'
actionpack (4.0.1) lib/action_dispatch/routing/route_set.rb:80:in `call'
actionpack (4.0.1) lib/action_dispatch/routing/route_set.rb:80:in `dispatch'
actionpack (4.0.1) lib/action_dispatch/routing/route_set.rb:48:in `call'
actionpack (4.0.1) lib/action_dispatch/journey/router.rb:71:in `block in call'
actionpack (4.0.1) lib/action_dispatch/journey/router.rb:59:in `each'
actionpack (4.0.1) lib/action_dispatch/journey/router.rb:59:in `call'
actionpack (4.0.1) lib/action_dispatch/routing/route_set.rb:680:in `call'
rack (1.6.4) lib/rack/deflater.rb:35:in `call'
warden (1.2.3) lib/warden/manager.rb:35:in `block in call'
warden (1.2.3) lib/warden/manager.rb:34:in `catch'
warden (1.2.3) lib/warden/manager.rb:34:in `call'
rack (1.6.4) lib/rack/etag.rb:24:in `call'
rack (1.6.4) lib/rack/conditionalget.rb:38:in `call'
rack (1.6.4) lib/rack/head.rb:13:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/params_parser.rb:27:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/flash.rb:241:in `call'
rack (1.6.4) lib/rack/session/abstract/id.rb:225:in `context'
rack (1.6.4) lib/rack/session/abstract/id.rb:220:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/cookies.rb:486:in `call'
activerecord (4.0.1) lib/active_record/query_cache.rb:36:in `call'
activerecord (4.0.1)   lib/active_record/connection_adapters/abstract/connection_pool.rb:626:in `call'
activerecord (4.0.1) lib/active_record/migration.rb:369:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
activesupport (4.0.1) lib/active_support/callbacks.rb:373:in `_run__753779113942060240__call__callbacks'
activesupport (4.0.1) lib/active_support/callbacks.rb:80:in `run_callbacks'
actionpack (4.0.1) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/reloader.rb:64:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/remote_ip.rb:76:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/debug_exceptions.rb:17:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
railties (4.0.1) lib/rails/rack/logger.rb:38:in `call_app'
railties (4.0.1) lib/rails/rack/logger.rb:20:in `block in call'
activesupport (4.0.1) lib/active_support/tagged_logging.rb:67:in `block in tagged'
activesupport (4.0.1) lib/active_support/tagged_logging.rb:25:in `tagged'
activesupport (4.0.1) lib/active_support/tagged_logging.rb:67:in `tagged'
railties (4.0.1) lib/rails/rack/logger.rb:20:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/request_id.rb:21:in `call'
rack (1.6.4) lib/rack/methodoverride.rb:22:in `call'
rack (1.6.4) lib/rack/runtime.rb:18:in `call'
activesupport (4.0.1) lib/active_support/cache/strategy/local_cache.rb:83:in `call'
rack (1.6.4) lib/rack/lock.rb:17:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/static.rb:64:in `call'
rack (1.6.4) lib/rack/sendfile.rb:113:in `call'
railties (4.0.1) lib/rails/engine.rb:511:in `call'
railties (4.0.1) lib/rails/application.rb:97:in `call'
rack (1.6.4) lib/rack/tempfile_reaper.rb:15:in `call'
rack (1.6.4) lib/rack/lint.rb:49:in `_call'
rack (1.6.4) lib/rack/lint.rb:37:in `call'
rack (1.6.4) lib/rack/showexceptions.rb:24:in `call'
rack (1.6.4) lib/rack/commonlogger.rb:33:in `call'
rack (1.6.4) lib/rack/chunked.rb:54:in `call'
rack (1.6.4) lib/rack/content_length.rb:15:in `call'
unicorn (5.0.0) lib/unicorn/http_server.rb:562:in `process_client'
unicorn (5.0.0) lib/unicorn/http_server.rb:658:in `worker_loop'
unicorn (5.0.0) lib/unicorn/http_server.rb:508:in `spawn_missing_workers'
unicorn (5.0.0) lib/unicorn/http_server.rb:132:in `start'
unicorn (5.0.0) bin/unicorn:126:in `<top (required)>'
/usr/local/rvm/gems/ruby-2.2.1/bin/unicorn:23:in `load'
/usr/local/rvm/gems/ruby-2.2.1/bin/unicorn:23:in `<main>'
/usr/local/rvm/gems/ruby-2.2.1@global/bin/ruby_executable_hooks:15:in `eval'
/usr/local/rvm/gems/ruby-2.2.1@global/bin/ruby_executable_hooks:15:in `<main>'

activerecord（4.0.1）lib/active\u record/associations/has\u many\u association.rb:81:in`cached\u counter\u attribute\u name'
activerecord（4.0.1）lib/active\u record/associations/has\u many\u association.rb:104:在'inverse\u updates\u counter\u cache'中
activerecord（4.0.1）lib/active\u record/associations/has\u many\u association.rb:114:in'delete\u records'
activerecord（4.0.1）lib/active\u record/associations/collection\u association.rb:493:in'remove\u records'
activerecord（4.0.1）lib/active\u record/associations/collection\u association.rb:486:in'block in delete\u或销毁'
activerecord（4.0.1）lib/active\u record/associations/collection\u association.rb:152:in'block in transaction'
activerecord（4.0.1）lib/active\u record/connection\u adapters/abstract/database\u语句
activerecord（4.0.1）lib/active_record/transactions.rb:209:in'transaction'
activerecord（4.0.1）lib/active\u record/associations/collection\u association.rb:151:in'transaction'
activerecord（4.0.1）lib/active\u record/associations/collection\u association.rb:486:in'delete\u或\u destroy'
activerecord（4.0.1）lib/active\u record/associations/collection\u association.rb:247:in'destroy'
activerecord（4.0.1）lib/active\u record/associations/collection\u association.rb:170:in'destroy\u all'
activerecord（4.0.1）lib/active\u record/associations/has\u many\u association.rb:26:in'handle\u dependency'
activerecord（4.0.1）lib/active\u record/associations/builder/association.rb:97:in'has\u many\u dependent\u for\u assets'
activesupport（4.0.1）lib/active\u support/callbacks.rb:397:in``运行\uuuuuuuuuuuuuuu3353912714138952721\uuuuuuuuuuuu回调'
activesupport（4.0.1）lib/active\u support/callbacks.rb:80:in'run\u callbacks'
activerecord（4.0.1）lib/active_record/callbacks.rb:292:in'destroy'
activerecord（4.0.1）lib/active_record/transactions.rb:265:in'block in destroy'
activerecord（4.0.1）lib/active\u record/transactions.rb:326:in`block in with\u transaction\u returning\u status'
activerecord（4.0.1）lib/active\u record/connection\u adapters/abstract/database\u语句
activerecord（4.0.1）lib/active\u record/connection\u adapters/abstract/database\u statements.rb:210:in'within\u new\u transaction'
activerecord（4.0.1）lib/active\u record/connection\u adapters/abstract/database\u语句
activerecord（4.0.1）lib/active_record/transactions.rb:209:in'transaction'
activerecord（4.0.1）lib/active\u record/transactions.rb:323:in`with\u transaction\u returning\u status'
activerecord（4.0.1）lib/active_record/transactions.rb:265:in'destroy'
app/controllers/products\u controller.rb:225:在“销毁”中
actionpack（4.0.1）lib/action\u controller/metal/implicit\u render.rb:4:in'send\u action'
actionpack（4.0.1）lib/abstract\u controller/base.rb:189:in'process\u action'
actionpack（4.0.1）lib/action\u controller/metal/rendering.rb:10:in'process\u action'
actionpack（4.0.1）lib/abstract\u controller/callbacks.rb:18:in'block in process\u action'
activesupport（4.0.1）lib/active\u support/callbacks.rb:493:in`“u run\u 3348285909198205465\u process\u action\u callbacks”
activesupport（4.0.1）lib/active\u support/callbacks.rb:80:in'run\u callbacks'
actionpack（4.0.1）lib/abstract\u controller/callbacks.rb:17:in'process\u action'
actionpack（4.0.1）lib/action\u controller/metal/rescue.rb:29:in'process\u action'
actionpack（4.0.1）lib/action\u controller/metal/instrumentation.rb:31:in'block in process\u action'
activesupport（4.0.1）lib/active_support/notifications.rb:159:in'block in instrument'
activesupport（4.0.1）lib/active_support/notifications/instrumenter.rb:20:in'instrument'
activesupport（4.0.1）lib/active_support/notifications.rb:159:in'instrument'
actionpack（4.0.1）lib/action\u controller/metal/instrumentation.rb:30:in'process\u action'
actionpack（4.0.1）lib/action_controller/metal/params_wrapper.rb:245:in'process_action'
activerecord（4.0.1）lib/active\u record/railties/controller\u runtime.rb:18:in'process\u action'
actionpack（4.0.1）lib/abstract_controller/base.rb:136:在“进程”中
actionpack（4.0.1）lib/abstract_controller/rendering.rb:44:in'process'
actionpack（4.0.1）lib/action_controller/metal.rb:195:in'dispatch'
actionpack（4.0.1）lib/action\u controller/metal/rack\u delegation.rb:13:in'dispatch'
actionpack（4.0.1）lib/action_controller/metal.rb:231:in“block in action”
actionpack（4.0.1）lib/action\u dispatch/routing/route\u set.rb:80:in'call'
actionpack（4.0.1）lib/action\u dispatch/routing/route\u set.rb:80:in'dispatch'
actionpack（4.0.1）lib/action\u dispatch/routing/route\u set.rb:48:in'call'
actionpack（4.0.1）lib/action_dispatch/journey/router.rb:71:in'block in call'
actionpack（4.0.1）lib/action_dispatch/journey/router.rb:59:in'each'
actionpack（4.0.1）lib/action_dispatch/journey/router.rb:59:in'call'
actionpack（4.0.1）lib/action\u dispatch/routing/route\u set.rb:680:in'call'
机架（1.6.4）lib/rack/deflater.rb:35:in'call'
典狱长（1.2.3）lib/warden/manager.rb:35:in'block in call'
典狱长（1.2.3）lib/warden/manager.rb:34:in'catch'
典狱长（1.2.3）lib/warden/manager.rb:34:in'call'
机架（1.6.4）lib/rack/etag.rb:24:in'call'
rack（1.6.4）lib/rack/conditionalget.rb:38:in'call'
机架（1.6.4）lib/rack/head.rb:13:in'call'
actionpack（4.0.1）lib/action_dispatch/middleware/params_parser.rb:27:in'call'
actionpack（4.0.1）lib/action\u dispatch/middleware/flash.rb:241:in'call'
框架（1.6.4）lib/rack/session/abstract/id.rb:225:在“上下文”中
机架（1.6.4）lib/rack/session/abstract/id.rb:220:in'call'
actionpack（4.0.1）lib/action\u dispatch/middleware/cookies.rb:486:in'call'
activerecord（4.0.1）lib/active\u record/query\u cache.rb:36:in'call'
activerecord（4.0.1）lib/active\u record/connection\u adapters/abstract/connection\u pool.rb:626:in'call'
activerecord（4.0.1）lib/active_record/migration.rb:369:in'call'
actionpack（4.0.1）lib/action\u dispat
   app/controllers/products_controller.rb:225:in `destroy'

activerecord (4.0.1) lib/active_record/associations/has_many_association.rb:81:in `cached_counter_attribute_name'
activerecord (4.0.1) lib/active_record/associations/has_many_association.rb:104:in `inverse_updates_counter_cache?'
activerecord (4.0.1) lib/active_record/associations/has_many_association.rb:114:in `delete_records'
activerecord (4.0.1) lib/active_record/associations/collection_association.rb:493:in `remove_records'
activerecord (4.0.1) lib/active_record/associations/collection_association.rb:486:in `block in delete_or_destroy'
activerecord (4.0.1) lib/active_record/associations/collection_association.rb:152:in `block in transaction'
activerecord (4.0.1) lib/active_record/connection_adapters/abstract/database_statements.rb:200:in `transaction'
activerecord (4.0.1) lib/active_record/transactions.rb:209:in `transaction'
activerecord (4.0.1) lib/active_record/associations/collection_association.rb:151:in `transaction'
activerecord (4.0.1) lib/active_record/associations/collection_association.rb:486:in `delete_or_destroy'
activerecord (4.0.1) lib/active_record/associations/collection_association.rb:247:in `destroy'
activerecord (4.0.1)  lib/active_record/associations/collection_association.rb:170:in `destroy_all'
activerecord (4.0.1) lib/active_record/associations/has_many_association.rb:26:in `handle_dependency'
 activerecord (4.0.1) lib/active_record/associations/builder/association.rb:97:in `has_many_dependent_for_assets'
 activesupport (4.0.1) lib/active_support/callbacks.rb:397:in `_run__3353912714138952721__destroy__callbacks'
 activesupport (4.0.1) lib/active_support/callbacks.rb:80:in `run_callbacks'
 activerecord (4.0.1) lib/active_record/callbacks.rb:292:in `destroy'
 activerecord (4.0.1) lib/active_record/transactions.rb:265:in `block in destroy'
activerecord (4.0.1) lib/active_record/transactions.rb:326:in `block in with_transaction_returning_status'
activerecord (4.0.1) lib/active_record/connection_adapters/abstract/database_statements.rb:202:in `block in transaction'
activerecord (4.0.1) lib/active_record/connection_adapters/abstract/database_statements.rb:210:in `within_new_transaction'
activerecord (4.0.1) lib/active_record/connection_adapters/abstract/database_statements.rb:202:in `transaction'
activerecord (4.0.1) lib/active_record/transactions.rb:209:in `transaction'
activerecord (4.0.1) lib/active_record/transactions.rb:323:in `with_transaction_returning_status'
activerecord (4.0.1) lib/active_record/transactions.rb:265:in `destroy'
app/controllers/products_controller.rb:225:in `destroy'
    actionpack (4.0.1) lib/action_controller/metal/implicit_render.rb:4:in `send_action'
    actionpack (4.0.1) lib/abstract_controller/base.rb:189:in `process_action'
    actionpack (4.0.1) lib/action_controller/metal/rendering.rb:10:in `process_action'
    actionpack (4.0.1) lib/abstract_controller/callbacks.rb:18:in `block in process_action'
    activesupport (4.0.1) lib/active_support/callbacks.rb:493:in `_run__3348285909198205465__process_action__callbacks'
    activesupport (4.0.1) lib/active_support/callbacks.rb:80:in `run_callbacks'
    actionpack (4.0.1) lib/abstract_controller/callbacks.rb:17:in `process_action'
    actionpack (4.0.1) lib/action_controller/metal/rescue.rb:29:in `process_action'
    actionpack (4.0.1) lib/action_controller/metal/instrumentation.rb:31:in `block in process_action'
    activesupport (4.0.1) lib/active_support/notifications.rb:159:in `block in instrument'
    activesupport (4.0.1) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
    activesupport (4.0.1) lib/active_support/notifications.rb:159:in `instrument'
    actionpack (4.0.1) lib/action_controller/metal/instrumentation.rb:30:in `process_action'
    actionpack (4.0.1) lib/action_controller/metal/params_wrapper.rb:245:in `process_action'
    activerecord (4.0.1) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
    actionpack (4.0.1) lib/abstract_controller/base.rb:136:in `process'
 actionpack (4.0.1) lib/abstract_controller/rendering.rb:44:in `process'
actionpack (4.0.1) lib/action_controller/metal.rb:195:in `dispatch'
actionpack (4.0.1) lib/action_controller/metal/rack_delegation.rb:13:in `dispatch'
actionpack (4.0.1) lib/action_controller/metal.rb:231:in `block in action'
actionpack (4.0.1) lib/action_dispatch/routing/route_set.rb:80:in `call'
actionpack (4.0.1) lib/action_dispatch/routing/route_set.rb:80:in `dispatch'
actionpack (4.0.1) lib/action_dispatch/routing/route_set.rb:48:in `call'
actionpack (4.0.1) lib/action_dispatch/journey/router.rb:71:in `block in call'
actionpack (4.0.1) lib/action_dispatch/journey/router.rb:59:in `each'
actionpack (4.0.1) lib/action_dispatch/journey/router.rb:59:in `call'
actionpack (4.0.1) lib/action_dispatch/routing/route_set.rb:680:in `call'
rack (1.6.4) lib/rack/deflater.rb:35:in `call'
warden (1.2.3) lib/warden/manager.rb:35:in `block in call'
warden (1.2.3) lib/warden/manager.rb:34:in `catch'
warden (1.2.3) lib/warden/manager.rb:34:in `call'
rack (1.6.4) lib/rack/etag.rb:24:in `call'
rack (1.6.4) lib/rack/conditionalget.rb:38:in `call'
rack (1.6.4) lib/rack/head.rb:13:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/params_parser.rb:27:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/flash.rb:241:in `call'
rack (1.6.4) lib/rack/session/abstract/id.rb:225:in `context'
rack (1.6.4) lib/rack/session/abstract/id.rb:220:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/cookies.rb:486:in `call'
activerecord (4.0.1) lib/active_record/query_cache.rb:36:in `call'
activerecord (4.0.1)   lib/active_record/connection_adapters/abstract/connection_pool.rb:626:in `call'
activerecord (4.0.1) lib/active_record/migration.rb:369:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
activesupport (4.0.1) lib/active_support/callbacks.rb:373:in `_run__753779113942060240__call__callbacks'
activesupport (4.0.1) lib/active_support/callbacks.rb:80:in `run_callbacks'
actionpack (4.0.1) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/reloader.rb:64:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/remote_ip.rb:76:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/debug_exceptions.rb:17:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
railties (4.0.1) lib/rails/rack/logger.rb:38:in `call_app'
railties (4.0.1) lib/rails/rack/logger.rb:20:in `block in call'
activesupport (4.0.1) lib/active_support/tagged_logging.rb:67:in `block in tagged'
activesupport (4.0.1) lib/active_support/tagged_logging.rb:25:in `tagged'
activesupport (4.0.1) lib/active_support/tagged_logging.rb:67:in `tagged'
railties (4.0.1) lib/rails/rack/logger.rb:20:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/request_id.rb:21:in `call'
rack (1.6.4) lib/rack/methodoverride.rb:22:in `call'
rack (1.6.4) lib/rack/runtime.rb:18:in `call'
activesupport (4.0.1) lib/active_support/cache/strategy/local_cache.rb:83:in `call'
rack (1.6.4) lib/rack/lock.rb:17:in `call'
actionpack (4.0.1) lib/action_dispatch/middleware/static.rb:64:in `call'
rack (1.6.4) lib/rack/sendfile.rb:113:in `call'
railties (4.0.1) lib/rails/engine.rb:511:in `call'
railties (4.0.1) lib/rails/application.rb:97:in `call'
rack (1.6.4) lib/rack/tempfile_reaper.rb:15:in `call'
rack (1.6.4) lib/rack/lint.rb:49:in `_call'
rack (1.6.4) lib/rack/lint.rb:37:in `call'
rack (1.6.4) lib/rack/showexceptions.rb:24:in `call'
rack (1.6.4) lib/rack/commonlogger.rb:33:in `call'
rack (1.6.4) lib/rack/chunked.rb:54:in `call'
rack (1.6.4) lib/rack/content_length.rb:15:in `call'
unicorn (5.0.0) lib/unicorn/http_server.rb:562:in `process_client'
unicorn (5.0.0) lib/unicorn/http_server.rb:658:in `worker_loop'
unicorn (5.0.0) lib/unicorn/http_server.rb:508:in `spawn_missing_workers'
unicorn (5.0.0) lib/unicorn/http_server.rb:132:in `start'
unicorn (5.0.0) bin/unicorn:126:in `<top (required)>'
/usr/local/rvm/gems/ruby-2.2.1/bin/unicorn:23:in `load'
/usr/local/rvm/gems/ruby-2.2.1/bin/unicorn:23:in `<main>'
/usr/local/rvm/gems/ruby-2.2.1@global/bin/ruby_executable_hooks:15:in `eval'
/usr/local/rvm/gems/ruby-2.2.1@global/bin/ruby_executable_hooks:15:in `<main>'

class Item < ActiveRecord::Base
 belongs_to :user
 belongs_to :order
 belongs_to :product
end

class Cart < ActiveRecord::Base
  belongs_to :user
  belongs_to :product
end

class Asset < ActiveRecord::Base
 mount_uploader :asset1, AssetUploader
 mount_uploader :asset2, AssetUploader
 mount_uploader :asset3, AssetUploader
 mount_uploader :asset4, AssetUploader 
end