NoMethodError：nil的未定義方法'type'：Rails中的NilClass

Question

嘗試加載使用Rails構建的網站上的其中一個頁面時獲取NoMethodError。 請參閱下面的完整堆棧跟蹤。

如果我在production.rb中將false更改為true

config.cache_classes = false

然后問題消失了，但每次我對任何文件進行更改時，我都必須重新啟動Rails服務器。 似乎問題與檢查數據庫中列的類型有關，但我無法弄清楚如何解決它。

控制器動作：

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類型的 - 我認為這些列導致了問題，但我不完全確定。

完整堆棧跟蹤：

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

在我的例子中，我有一個包含76個屬性的模型，其中一個被命名為“class”，這導致了錯誤和異常。

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頭中重命名'class'
• rails g腳手架MyModel blablaba ..
• rake / bin db：migrate
• 導入數據
• 導軌

並且工作:-)

Answer 2

您的錯誤似乎與此錯誤有關 。 有一些建議的解決方案可能與您的情況相關，或者您可以嘗試alsemyonov的此修復程序 。

Answer 3

嘗試設置config.autoload_once_paths