NoMethodError：nil的未定义方法’type’：Rails中的NilClass

尝试加载使用Rails构建的网站上的其中一个页面时获取NoMethodError。 请参阅下面的完整堆栈跟踪。

如果我在production.rb中将false更改为true

 config.cache_classes = false 

然后问题消失了，但每次我对任何文件进行更改时，我都必须重新启动Rails服务器。 似乎问题与检查数据库中列的类型有关，但我无法弄清楚如何解决它。

控制器动作：

 def manage @view_data = {} if (@view_data[:product] = Product.find(params[:id])).nil? raise ActionController::RoutingError.new('Not Found') end @view_data[:backlog] = Task.where("product_id = ? AND status < ?", params[:id], Task::STATUS_COMPLETED) .page(params[:page]).per(10) @view_data[:completed] = Task.where(product_id: params[:id], status: Task::STATUS_COMPLETED) .page(params[:page]).per(10) end 

‘tasks’表上有四列是datetime类型的 – 我认为这些列导致了问题，但我不完全确定。

完整堆栈跟踪：

 NoMethodError - undefined method `type' for nil:NilClass: activerecord (3.2.13) lib/active_record/attribute_methods/time_zone_conversion.rb:60:in `create_time_zone_conversion_attribute?' activerecord (3.2.13) lib/active_record/attribute_methods/time_zone_conversion.rb:24:in `attribute_cast_code' activerecord (3.2.13) lib/active_record/attribute_methods/serialization.rb:80:in `attribute_cast_code' activerecord (3.2.13) lib/active_record/attribute_methods/read.rb:72:in `define_method_attribute' activerecord (3.2.13) lib/active_record/attribute_methods/primary_key.rb:29:in `define_method_attribute' activemodel (3.2.13) lib/active_model/attribute_methods.rb:267:in `block in define_attribute_method' activemodel (3.2.13) lib/active_model/attribute_methods.rb:260:in `define_attribute_method' activemodel (3.2.13) lib/active_model/attribute_methods.rb:256:in `block in define_attribute_methods' activemodel (3.2.13) lib/active_model/attribute_methods.rb:256:in `define_attribute_methods' activerecord (3.2.13) lib/active_record/attribute_methods.rb:66:in `block in define_attribute_methods' activerecord (3.2.13) lib/active_record/attribute_methods.rb:63:in `define_attribute_methods' activerecord (3.2.13) lib/active_record/attribute_methods.rb:168:in `respond_to?' activesupport (3.2.13) lib/active_support/callbacks.rb:398:in `__run_callback' activesupport (3.2.13) lib/active_support/callbacks.rb:385:in `_run_initialize_callbacks' activesupport (3.2.13) lib/active_support/callbacks.rb:81:in `run_callbacks' activerecord (3.2.13) lib/active_record/base.rb:501:in `initialize' app/controllers/products_controller.rb:14:in `manage' actionpack (3.2.13) lib/action_controller/metal/implicit_render.rb:4:in `send_action' actionpack (3.2.13) lib/abstract_controller/base.rb:167:in `process_action' actionpack (3.2.13) lib/action_controller/metal/rendering.rb:10:in `process_action' actionpack (3.2.13) lib/abstract_controller/callbacks.rb:18:in `block in process_action' activesupport (3.2.13) lib/active_support/callbacks.rb:425:in `_run__115665803178931257__process_action__4080704983955383443__callbacks' activesupport (3.2.13) lib/active_support/callbacks.rb:405:in `__run_callback' activesupport (3.2.13) lib/active_support/callbacks.rb:385:in `_run_process_action_callbacks' activesupport (3.2.13) lib/active_support/callbacks.rb:81:in `run_callbacks' actionpack (3.2.13) lib/abstract_controller/callbacks.rb:17:in `process_action' actionpack (3.2.13) lib/action_controller/metal/rescue.rb:29:in `process_action' actionpack (3.2.13) lib/action_controller/metal/instrumentation.rb:30:in `block in process_action' activesupport (3.2.13) lib/active_support/notifications.rb:123:in `block in instrument' activesupport (3.2.13) lib/active_support/notifications/instrumenter.rb:20:in `instrument' activesupport (3.2.13) lib/active_support/notifications.rb:123:in `instrument' actionpack (3.2.13) lib/action_controller/metal/instrumentation.rb:29:in `process_action' actionpack (3.2.13) lib/action_controller/metal/params_wrapper.rb:207:in `process_action' activerecord (3.2.13) lib/active_record/railties/controller_runtime.rb:18:in `process_action' actionpack (3.2.13) lib/abstract_controller/base.rb:121:in `process' actionpack (3.2.13) lib/abstract_controller/rendering.rb:45:in `process' actionpack (3.2.13) lib/action_controller/metal.rb:203:in `dispatch' actionpack (3.2.13) lib/action_controller/metal/rack_delegation.rb:14:in `dispatch' actionpack (3.2.13) lib/action_controller/metal.rb:246:in `block in action' actionpack (3.2.13) lib/action_dispatch/routing/route_set.rb:73:in `dispatch' actionpack (3.2.13) 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 `call' actionpack (3.2.13) lib/action_dispatch/routing/route_set.rb:612:in `call' actionpack (3.2.13) lib/action_dispatch/middleware/best_standards_support.rb:17:in `call' rack (1.4.5) lib/rack/etag.rb:23:in `call' rack (1.4.5) lib/rack/conditionalget.rb:25:in `call' actionpack (3.2.13) lib/action_dispatch/middleware/head.rb:14:in `call' actionpack (3.2.13) lib/action_dispatch/middleware/params_parser.rb:21:in `call' actionpack (3.2.13) lib/action_dispatch/middleware/flash.rb:242:in `call' rack (1.4.5) lib/rack/session/abstract/id.rb:210:in `context' rack (1.4.5) lib/rack/session/abstract/id.rb:205:in `call' actionpack (3.2.13) lib/action_dispatch/middleware/cookies.rb:341:in `call' activerecord (3.2.13) lib/active_record/query_cache.rb:64:in `call' activerecord (3.2.13) lib/active_record/connection_adapters/abstract/connection_pool.rb:479:in `call' actionpack (3.2.13) lib/action_dispatch/middleware/callbacks.rb:28:in `block in call' activesupport (3.2.13) lib/active_support/callbacks.rb:405:in `_run__4157597128006817714__call__2909158845673021585__callbacks' activesupport (3.2.13) lib/active_support/callbacks.rb:405:in `__run_callback' activesupport (3.2.13) lib/active_support/callbacks.rb:385:in `_run_call_callbacks' activesupport (3.2.13) lib/active_support/callbacks.rb:81:in `run_callbacks' actionpack (3.2.13) lib/action_dispatch/middleware/callbacks.rb:27:in `call' actionpack (3.2.13) lib/action_dispatch/middleware/remote_ip.rb:31:in `call' better_errors (0.9.0) lib/better_errors/middleware.rb:84:in `protected_app_call' better_errors (0.9.0) lib/better_errors/middleware.rb:79:in `better_errors_call' better_errors (0.9.0) lib/better_errors/middleware.rb:56:in `call' actionpack (3.2.13) lib/action_dispatch/middleware/debug_exceptions.rb:16:in `call' actionpack (3.2.13) lib/action_dispatch/middleware/show_exceptions.rb:56:in `call' railties (3.2.13) lib/rails/rack/logger.rb:32:in `call_app' railties (3.2.13) lib/rails/rack/logger.rb:16:in `block in call' activesupport (3.2.13) lib/active_support/tagged_logging.rb:22:in `tagged' railties (3.2.13) lib/rails/rack/logger.rb:16:in `call' actionpack (3.2.13) lib/action_dispatch/middleware/request_id.rb:22:in `call' rack (1.4.5) lib/rack/methodoverride.rb:21:in `call' rack (1.4.5) lib/rack/runtime.rb:17:in `call' activesupport (3.2.13) lib/active_support/cache/strategy/local_cache.rb:72:in `call' rack (1.4.5) lib/rack/lock.rb:15:in `call' actionpack (3.2.13) lib/action_dispatch/middleware/static.rb:63:in `call' railties (3.2.13) lib/rails/engine.rb:479:in `call' railties (3.2.13) lib/rails/application.rb:223:in `call' rack (1.4.5) lib/rack/content_length.rb:14:in `call' railties (3.2.13) lib/rails/rack/log_tailer.rb:17:in `call' rack (1.4.5) lib/rack/handler/webrick.rb:59:in `service' 

Answer 1

在我的情况下，我有一个具有76个属性的模型，其中一个被命名为“类”，这导致错误和exception。

所以我做了：

• rake / bin db：rollback
• rails d scaffold MyModel
• 在scaffold generator命令中重命名’class’列
• 在csv头中重命名’class’
• rails g脚手架MyModel blablaba ..
• rake / bin db：migrate
• 导入数据
• 导轨

并且工作:-)

Answer 2

您的错误似乎与此错误有关 。 有一些建议的解决方案可能与您的情况相关，或者您可以尝试alsemyonov的此修复程序 。

Answer 3

尝试设置config.autoload_once_paths