引用 devise gem 的 controller generator 源 代码 ：

Create inherited Devise controllers in your app/controllers folder.

   Use -c to specify which controller you want to overwrite.
   If you do no specify a controller, all controllers will be created.
   For example:

     rails generate devise:controllers users -c=sessions

   This will create a controller class at app/controllers/users/sessions_controller.rb like this:

     class Users::SessionsController < Devise::SessionsController
       content...
     end

中 的 每 一 个