Devise取り消す作業

メモ

Use the generator to remove configuration files as well (step 2), so the whole process would be (referencing previous answers):

1. Remove the table: rake db:rollback VERSION=<insert the version number of the migration>
2. Remove the configuration: rails destroy devise:install
3. Remove your User model: rails destroy devise User (replace 'User' with the name of your model)
4. Remove references to devise in your routes.rb, gemfile, controller files, and view files like the following, if you used them (once again replacing 'user' with your model name):
   • devise_for (routes.rb)
   • gem 'devise' (gemfile)
   • before_action :authenticate_user! (controllers)
   • user_signed_in? (controllers, views)
   • current_user (controllers, views)
   • user_session (controllers, views)

confi/routes.rb の中のdevise関係削除する

引用元: Ruby: how to uninstall Devise? - Stack Overflow