Rails understands GET request but not POST request

When I access /users/registration/sign_up in my app via the browser (GET) a page renders. When I do the same thing via POST (either by submitting a form w/ the target /users/registration/sign_up or with ajax) my app returns the following error:

Unknown action The action 'registration' could not be found for UsersController

I am using devise for authentication and creating a devise route for my User model using:

devise_for :users

This path should route to the devise/registrations_controller where i expect it to execute the new method (it currently does for a GET request). Maybe rails, understanding the request is a POST request automatically directs it to the create method but I don't think this is the issue because I start the debugger first thing in the create method and the debugger is not starting in my terminal befo开发者_如何转开发re I receive this error.

Can anyone with experience with devise decipher what's going on? I'm happy to provide more info if necessary. Thanks.

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Devise adds routes to your Rails app, which you can see by running rake routes from a terminal:

      new_user_session GET    /users/sign_in(.:format)
          user_session POST   /users/sign_in(.:format)
  destroy_user_session GET    /users/sign_out(.:format)
         user_password POST   /users/password(.:format)
     new_user_password GET    /users/password/new(.:format)
    edit_user_password GET    /users/password/edit(.:format)
                       PUT    /users/password(.:format)
     user_registration POST   /users(.:format)
 new_user_registration GET    /users/sign_up(.:format)
edit_user_registration GET    /users/edit(.:format)
                       PUT    /users(.:format)
                       DELETE /users(.:format)
                  root        /(.:format)

And as you discovered, there is a GET /users/sign_up but no POST /users/sign_up. When creating Devise expects POST /users, for which you can use the helper method user_registration_path. This gets handled by Devise::RegistrationsController#create.