我有一个最近开始的项目，我使用 mongoid 作为数据库并使用 rails_admin 来管理它，现在我想要一个 api 并且我选择 rails-api 来做它，但由于某种原因，因为我刚刚添加了 rails- api到gem文件，我无法访问管理员，我总是收到这个错误
设计中的 NoMethodError::SessionsController#new
nil:NilClass 的未定义方法“[]”
这是痕迹
warden (1.1.1) lib/warden/session_serializer.rb:29:in fetch'
warden (1.1.1) lib/warden/proxy.rb:196:inuser'warden (1.1.1) lib/warden/proxy.rb:293:in _perform_authentication'
warden (1.1.1) lib/warden/proxy.rb:90:inauthenticate'warden (1.1.1) lib/warden/proxy。 rb:100:in authenticate?'
devise (2.1.0) app/controllers/devise_controller.rb:113:inrequire_no_authentication' activesupport (3.2.5) lib/active_support/callbacks.rb:407:in _run__3280997315660744487__process_action__4533000551616940901__callbacks'
activesupport (3.2.5) lib/active_support/callbacks.rb:405:in__run_callback' activesupport (3.2.5) lib/active_support/callbacks.rb:385:in _run_process_action_callbacks'
activesupport (3.2.5) lib/active_support/callbacks.rb:81:inrun_callbacks' actionpack (3.2.5 ) lib/abstract_controller/callbacks.rb:17:in process_action'
actionpack (3.2.5) lib/action_controller/metal/rescue.rb:29:inprocess_action' actionpack (3.2.5) lib/action_controller/metal/instrumentation.rb:30:in block in process_action'
activesupport (3.2.5) lib/active_support/notifications.rb:123:inblock in instrument' activesupport (3.2.5) lib/active_support/notifications/instrumenter .rb:20:ininstrument'
activesupport (3.2.5) lib/active_support/notifications.rb:123:in仪器动作包 (3.2.5) lib/action_controller/metal/instrumentation.rb:29:inprocess_action'
actionpack (3.2.5) lib/action_controller/metal/params_wrapper.rb:206:inprocess_action' actionpack (3.2.5) lib/abstract_controller/base.rb:121:in process'
actionpack (3.2.5) lib/abstract_controller/rendering.rb:45:inprocess' actionpack (3.2.5) lib/action_controller/metal.rb:203:in dispatch'
actionpack (3.2.5) lib/action_controller/metal/rack_delegation.rb:14:indispatch' actionpack (3.2.5) lib/action_controller/ metal.rb:246:in block in action'
actionpack (3.2.5) lib/action_dispatch/routing/route_set.rb:73:incall' actionpack (3.2.5) lib/action_dispatch/routing/route_set.rb:73:in dispatch'
actionpack (3.2.5) lib/action_dispatch/routing/route_set.rb:36:incall' actionpack (3.2.5) lib/action_dispatch/routing/mapper.rb:42:incall'
journey (1.0.3) lib/journey/router.rb:68:in块in call' 旅程 (1.0.3) lib/journey/router.rb:56:in each'
journey (1.0.3) lib/journey/router.rb:56:incall' actionpack (3.2.5) lib/action_dispatch/routing/route_set.rb:600:in call'
rack-pjax (0.5.9) lib/rack/pjax.rb:12:incall' mongoid (2.4.10) lib /rack/mongoid/middleware/identity_map.rb:33:in block in call'
mongoid (2.4.10) lib/mongoid.rb:133:inunit_of_work' mongoid (2.4.10) lib/rack/mongoid/middleware/identity_map.rb:33:in call'
warden (1.1.1) lib/warden/manager.rb:35:inblock in call'warden (1.1.1) lib/warden /manager.rb:34:incatch'
warden (1.1.1) lib/warden/manager.rb:34:incall' rack (1.4.1) lib/rack/etag.rb:23:in call'
rack (1.4.1) lib/rack/conditionalget.rb:25:incall' actionpack (3.2.5) lib/action_dispatch/middleware/head.rb:14:in call'
remotipart (1.0.2) lib/remotipart/middleware.rb:30:incall' actionpack (3.2.5) lib/ action_dispatch/middleware/params_parser.rb:21:in call'
actionpack (3.2.5) lib/action_dispatch/middleware/callbacks.rb:28:inblock in call'activesupport (3.2.5) lib/active_support/callbacks.rb:405:in _run__2911892753477349565__call__1112249857594481255__callbacks'
activesupport (3.2.5) lib/active_support/callbacks.rb:405:in__run_callback' activesupport (3.2.5) lib/active_support/callbacks.rb:385:在_run_call_callbacks'
activesupport (3.2.5) lib/active_support/callbacks.rb:81:inrun_callbacks'actionpack (3.2.5) lib/action_dispatch/middleware/callbacks.rb:27:in call'
actionpack (3.2.5) lib/action_dispatch/middleware/reloader.rb:65:incall' actionpack (3.2.5) lib/action_dispatch/middleware/remote_ip.rb:31:in call'
actionpack (3.2.5) lib/action_dispatch/middleware/debug_exceptions.rb:16:incall' actionpack (3.2.5 ) lib/action_dispatch/middleware/show_exceptions.rb:56:in call'
railties (3.2.5) lib/rails/rack/logger.rb:26:incall_app' railties (3.2.5) lib/rails/rack/logger.rb:16:in call'
actionpack (3.2.5) lib/action_dispatch/middleware/request_id.rb:22:incall' rack (1.4.1) lib/rack/runtime.rb :17:在call'
activesupport (3.2.5) lib/active_support/cache/strategy/local_cache.rb:72:incall' rack (1.4.1) lib/rack/lock.rb:15:in call'
actionpack (3.2.5) lib/action_dispatch/middleware/static.rb:62:incall' railties (3.2.5) lib/rails/engine.rb:479:in call'
railties (3.2.5) lib/rails/application.rb:220:incall' rack (1.4.1) lib/rack/ content_length.rb:14:in call'
railties (3.2.5) lib/rails/rack/log_tailer.rb:17:incall' rack (1.4.1) lib/rack/handler/webrick.rb:59:in `service'
我真的不知道导致这种情况的那些宝石之间发生了什么，欢迎任何建议或指导；）