另一个nooby问题 - 我的项目中有这两个模型：
class Invoice < ActiveRecord::Base
has_many :items
end
和
class Item < ActiveRecord::Base
belongs_to :invoice ,:foreign_key=>'invoice_number',:primary_key=>'invoice_number'
end
因此，在我的控制器中，我想通过按下绑定到操作的按钮将新项目添加到发票中。该操作将生成一个表单，让客户填写有关项目的信息。我想在控制器中这样做：
@invoice.items << Item.new
这个操作可能是错误的，但问题是，Rails 告诉我有未定义的方法“项目”。有人可以给我一个关于如何解决这个问题的提示吗？
这是错误跟踪：
activemodel (3.2.8) lib/active_model/attribute_methods.rb:407:in `method_missing'
activerecord (3.2.8) lib/active_record/attribute_methods.rb:149:in `method_missing'
app/controllers/return_controller.rb:4:in `index'
actionpack (3.2.8) lib/action_controller/metal/implicit_render.rb:4:in `send_action'
actionpack (3.2.8) lib/abstract_controller/base.rb:167:in `process_action'
actionpack (3.2.8) lib/action_controller/metal/rendering.rb:10:in `process_action'
actionpack (3.2.8) lib/abstract_controller/callbacks.rb:18:in `block in process_action'
activesupport (3.2.8) lib/active_support/callbacks.rb:414:in `_run__3004877794972512718__process_action__435319474484567757__callbacks'
activesupport (3.2.8) lib/active_support/callbacks.rb:405:in `__run_callback'
activesupport (3.2.8) lib/active_support/callbacks.rb:385:in `_run_process_action_callbacks'
activesupport (3.2.8) lib/active_support/callbacks.rb:81:in `run_callbacks'
actionpack (3.2.8) lib/abstract_controller/callbacks.rb:17:in `process_action'
actionpack (3.2.8) lib/action_controller/metal/rescue.rb:29:in `process_action'
actionpack (3.2.8) lib/action_controller/metal/instrumentation.rb:30:in `block in process_action'
activesupport (3.2.8) lib/active_support/notifications.rb:123:in `block in instrument'
activesupport (3.2.8) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
activesupport (3.2.8) lib/active_support/notifications.rb:123:in `instrument'
actionpack (3.2.8) lib/action_controller/metal/instrumentation.rb:29:in `process_action'
actionpack (3.2.8) lib/action_controller/metal/params_wrapper.rb:207:in `process_action'
activerecord (3.2.8) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
actionpack (3.2.8) lib/abstract_controller/base.rb:121:in `process'
actionpack (3.2.8) lib/abstract_controller/rendering.rb:45:in `process'
actionpack (3.2.8) lib/action_controller/metal.rb:203:in `dispatch'
actionpack (3.2.8) lib/action_controller/metal/rack_delegation.rb:14:in `dispatch'
actionpack (3.2.8) lib/action_controller/metal.rb:246:in `block in action'
actionpack (3.2.8) lib/action_dispatch/routing/route_set.rb:73:in `call'
actionpack (3.2.8) lib/action_dispatch/routing/route_set.rb:73:in `dispatch'
actionpack (3.2.8) lib/action_dispatch/routing/route_set.rb:36:in `call'
journey (1.0.4) lib/journey/router.rb:68:in `block in call'
journey (1.0.4) lib/journey/router.rb:56:in `each'
journey (1.0.4) lib/journey/router.rb:56:in `call'
actionpack (3.2.8) lib/action_dispatch/routing/route_set.rb:600:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/best_standards_support.rb:17:in `call'
rack (1.4.1) lib/rack/etag.rb:23:in `call'
rack (1.4.1) lib/rack/conditionalget.rb:25:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/head.rb:14:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/params_parser.rb:21:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/flash.rb:242:in `call'
rack (1.4.1) lib/rack/session/abstract/id.rb:205:in `context'
rack (1.4.1) lib/rack/session/abstract/id.rb:200:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/cookies.rb:339:in `call'
activerecord (3.2.8) lib/active_record/query_cache.rb:64:in `call'
activerecord (3.2.8) lib/active_record/connection_adapters/abstract/connection_pool.rb:473:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/callbacks.rb:28:in `block in call'
activesupport (3.2.8) lib/active_support/callbacks.rb:405:in `_run__2876506060705866238__call__963306619056181882__callbacks'
activesupport (3.2.8) lib/active_support/callbacks.rb:405:in `__run_callback'
activesupport (3.2.8) lib/active_support/callbacks.rb:385:in `_run_call_callbacks'
activesupport (3.2.8) lib/active_support/callbacks.rb:81:in `run_callbacks'
actionpack (3.2.8) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/reloader.rb:65:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/remote_ip.rb:31:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/debug_exceptions.rb:16:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/show_exceptions.rb:56:in `call'
railties (3.2.8) lib/rails/rack/logger.rb:26:in `call_app'
railties (3.2.8) lib/rails/rack/logger.rb:16:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/request_id.rb:22:in `call'
rack (1.4.1) lib/rack/methodoverride.rb:21:in `call'
rack (1.4.1) lib/rack/runtime.rb:17:in `call'
activesupport (3.2.8) lib/active_support/cache/strategy/local_cache.rb:72:in `call'
rack (1.4.1) lib/rack/lock.rb:15:in `call'
actionpack (3.2.8) lib/action_dispatch/middleware/static.rb:62:in `call'
railties (3.2.8) lib/rails/engine.rb:479:in `call'
railties (3.2.8) lib/rails/application.rb:223:in `call'
rack (1.4.1) lib/rack/content_length.rb:14:in `call'
railties (3.2.8) lib/rails/rack/log_tailer.rb:17:in `call'
rack (1.4.1) lib/rack/handler/webrick.rb:59:in `service'
/usr/lib/ruby/1.9.1/webrick/httpserver.rb:138:in `service'
/usr/lib/ruby/1.9.1/webrick/httpserver.rb:94:in `run'
/usr/lib/ruby/1.9.1/webrick/server.rb:191:in `block in start_thread'
在控制台中它说：
NoMethodError (undefined method `items' for #<Invoice:0x00000002b822c8>):
app/controllers/invoice_controller.rb:4:in `index'
问题反馈： 感谢你们帮助我解决这个问题。我已经解决了这个问题 - 我发现了一个拼写错误（缺少 's'），很抱歉耽误了您的时间。再次感谢