在你的routes.rb文件，尝试包装你的路由在范围块内的错误消息建议。
下面是一个例子：

  devise_scope：user do 
 getsignup，to：devise / registrations＃new
 getlogin，to：devise / sessions＃new
 getlogout，to：devise / sessions＃destroy
 end 
 

这将给你很好地命名的路线。

顺便说一句，如果你使用Rails 4，摆脱匹配方法。您需要指定HTTP动词。

---

OBSOLETE旧答案：

使用上面的代码。）

  devise_for：users，path_names：{sign_in：' login'，sign_out：'logout'，sign_up：'signup'} 
 

AND

  match'/ sessions / user'，to：'devise / sessions＃create'，via：：post 
 

Very frustrating for the last few days.

I have a rails app with Devise installed where I generated a new User model and I generated Devise views as well.

This happens when I try to sign in as an existing user right when I click "Log in" after filling out the email and password fields:

AbstractController::ActionNotFound - Could not find devise mapping for path "/sessions/user".
This may happen for two reasons:

1) You forgot to wrap your route inside the scope block. For example:

  devise_scope :user do
    get "/some/route" => "some_devise_controller"
  end

2) You are testing a Devise controller bypassing the router.
   If so, you can explicitly tell Devise which mapping to use:

   @request.env["devise.mapping"] = Devise.mappings[:user]

:
  devise (3.2.4) app/controllers/devise_controller.rb:84:in `unknown_action!'
  devise (3.2.4) app/controllers/devise_controller.rb:59:in `assert_is_devise_resource!'
  devise (3.2.4) app/controllers/devise_controller.rb:97:in `require_no_authentication'
  activesupport (4.0.4) lib/active_support/callbacks.rb:397:in `_run__1955514966561508052__process_action__callbacks'
  activesupport (4.0.4) lib/active_support/callbacks.rb:80:in `run_callbacks'
  actionpack (4.0.4) lib/abstract_controller/callbacks.rb:17:in `process_action'
  actionpack (4.0.4) lib/action_controller/metal/rescue.rb:29:in `process_action'
  actionpack (4.0.4) lib/action_controller/metal/instrumentation.rb:31:in `block in process_action'
  activesupport (4.0.4) lib/active_support/notifications.rb:159:in `block in instrument'
  activesupport (4.0.4) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
  activesupport (4.0.4) lib/active_support/notifications.rb:159:in `instrument'
  actionpack (4.0.4) lib/action_controller/metal/instrumentation.rb:30:in `process_action'
  actionpack (4.0.4) lib/action_controller/metal/params_wrapper.rb:250:in `process_action'
  activerecord (4.0.4) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
  actionpack (4.0.4) lib/abstract_controller/base.rb:136:in `process'
  actionpack (4.0.4) lib/abstract_controller/rendering.rb:44:in `process'
  actionpack (4.0.4) lib/action_controller/metal.rb:195:in `dispatch'
  actionpack (4.0.4) lib/action_controller/metal/rack_delegation.rb:13:in `dispatch'
  actionpack (4.0.4) lib/action_controller/metal.rb:231:in `block in action'
  actionpack (4.0.4) lib/action_dispatch/routing/route_set.rb:80:in `dispatch'
  actionpack (4.0.4) lib/action_dispatch/routing/route_set.rb:48:in `call'
  actionpack (4.0.4) lib/action_dispatch/journey/router.rb:71:in `block in call'
  actionpack (4.0.4) lib/action_dispatch/journey/router.rb:59:in `call'
  actionpack (4.0.4) lib/action_dispatch/routing/route_set.rb:674: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 `call'
  rack (1.5.2) lib/rack/etag.rb:23:in `call'
  rack (1.5.2) lib/rack/conditionalget.rb:35:in `call'
  rack (1.5.2) lib/rack/head.rb:11:in `call'
  actionpack (4.0.4) lib/action_dispatch/middleware/params_parser.rb:27:in `call'
  actionpack (4.0.4) lib/action_dispatch/middleware/flash.rb:241:in `call'
  rack (1.5.2) lib/rack/session/abstract/id.rb:225:in `context'
  rack (1.5.2) lib/rack/session/abstract/id.rb:220:in `call'
  actionpack (4.0.4) lib/action_dispatch/middleware/cookies.rb:486:in `call'
  activerecord (4.0.4) lib/active_record/query_cache.rb:36:in `call'
  activerecord (4.0.4) lib/active_record/connection_adapters/abstract/connection_pool.rb:626:in `call'
  activerecord (4.0.4) lib/active_record/migration.rb:373:in `call'
  actionpack (4.0.4) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
  activesupport (4.0.4) lib/active_support/callbacks.rb:373:in `_run__2142997860843545523__call__callbacks'
  activesupport (4.0.4) lib/active_support/callbacks.rb:80:in `run_callbacks'
  actionpack (4.0.4) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
  actionpack (4.0.4) lib/action_dispatch/middleware/reloader.rb:64:in `call'
  actionpack (4.0.4) lib/action_dispatch/middleware/remote_ip.rb:76:in `call'
  better_errors (1.1.0) lib/better_errors/middleware.rb:84:in `protected_app_call'
  better_errors (1.1.0) lib/better_errors/middleware.rb:79:in `better_errors_call'
  better_errors (1.1.0) lib/better_errors/middleware.rb:56:in `call'
  actionpack (4.0.4) lib/action_dispatch/middleware/debug_exceptions.rb:17:in `call'
  actionpack (4.0.4) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
  railties (4.0.4) lib/rails/rack/logger.rb:38:in `call_app'
  railties (4.0.4) lib/rails/rack/logger.rb:20:in `block in call'
  activesupport (4.0.4) lib/active_support/tagged_logging.rb:68:in `block in tagged'
  activesupport (4.0.4) lib/active_support/tagged_logging.rb:26:in `tagged'
  activesupport (4.0.4) lib/active_support/tagged_logging.rb:68:in `tagged'
  railties (4.0.4) lib/rails/rack/logger.rb:20:in `call'
  quiet_assets (1.0.2) lib/quiet_assets.rb:18:in `call_with_quiet_assets'
  actionpack (4.0.4) lib/action_dispatch/middleware/request_id.rb:21:in `call'
  rack (1.5.2) lib/rack/methodoverride.rb:21:in `call'
  rack (1.5.2) lib/rack/runtime.rb:17:in `call'
  activesupport (4.0.4) lib/active_support/cache/strategy/local_cache.rb:83:in `call'
  rack (1.5.2) lib/rack/lock.rb:17:in `call'
  actionpack (4.0.4) lib/action_dispatch/middleware/static.rb:64:in `call'
  rack (1.5.2) lib/rack/sendfile.rb:112:in `call'
  railties (4.0.4) lib/rails/engine.rb:511:in `call'
  railties (4.0.4) lib/rails/application.rb:97:in `call'
  rack (1.5.2) lib/rack/lock.rb:17:in `call'
  rack (1.5.2) lib/rack/content_length.rb:14:in `call'
  rack (1.5.2) lib/rack/handler/webrick.rb:60:in `service'
  /Users/AaronWilliamson/.rubies/ruby-2.1.0/lib/ruby/2.1.0/webrick/httpserver.rb:138:in `service'
  /Users/AaronWilliamson/.rubies/ruby-2.1.0/lib/ruby/2.1.0/webrick/httpserver.rb:94:in `run'
  /Users/AaronWilliamson/.rubies/ruby-2.1.0/lib/ruby/2.1.0/webrick/server.rb:295:in `block in start_thread'

The thing is, when I sign up as a new user, it works just fine. I can fill in the appropriate fields, click "Sign up" and it notifies me that I've logged in successfully and redirects me to the root URL showing the user as logged in. The error only occurs when I try to log in.

Here are my routes:

Ripelist::Application.routes.draw do
  devise_for :users, path_names: { sign_in: 'login', sign_out: 'logout', sign_up: 'signup' }
  root to: 'listings#index'
  match '/sessions/user', to: 'devise/sessions#create', via: :post

  resources :users
  resources :listings
  resources :categories
  resources :sessions
end

Can anybody help?

in your routes.rb file, try wrapping your routes inside the scope block as the error message suggests. Here is an example:

devise_scope :user do
   get "signup", to: "devise/registrations#new"
   get "login", to: "devise/sessions#new"
   get "logout", to: "devise/sessions#destroy"
end

This will give you nicely named routes.

And by the way, if you are using Rails 4, get rid of the match method. you need to specify the HTTP verb.

---

OBSOLETE old answer:

(Below is the old obsolete version of the code, shown for reference. Use the code above.)

devise_for :users, path_names: { sign_in: 'login', sign_out: 'logout', sign_up: 'signup' }

AND

match '/sessions/user', to: 'devise/sessions#create', via: :post