Removing a Model in Rails (Reverse of "Rails G Model Title...")

How to reverse a 'rails generate'

rails destroy controller lalala
rails destroy model yadayada
rails destroy scaffold hohoho

Rails 3.2 adds a new d shortcut to the command, so now you can write:

rails d controller lalala
rails d model yadayada
rails d scaffold hohoho

What is the best way to drop a table & remove a model in Rails 3?

The second method is the ideal way to handle this: your migration files are meant to represent how your database has changed over time. The older migration files will remain in your project (in case, hypothetically, you wanted to roll back to an older version), but Rails will not run them when you rake db:migrate because it knows they've already been run (based on data in the database's schema_migrations table).

Your schema.rb will just be updated once to reflect that your database no longer contains that table.

One minor tweak to your code: your migration file should drop the table in the up method, and ideally recreate it in the down method. The "up" signifies that your migration drops the table to move forward in time, and if the migration is rolled back, the down method will be run.

Undo scaffolding in Rails

First, if you have already run the migrations generated by the scaffold command, you have to perform a rollback first.

rake db:rollback

You can create scaffolding using:

rails generate scaffold MyFoo 

(or similar), and you can destroy/undo it using

rails destroy scaffold MyFoo

That will delete all the files created by generate, but not any additional changes you may have made manually.

Rails destroy scaffold without previous rails g scaffold

I discover that destroy scaffold, only generetes paths to remove files, for example:

rails d scaffold my_directory/something

That generetes the next output in console:

    invoke  active_record
      remove    db/migrate/20170901061811_create_my_directory_somethings.rb
      remove    app/models/my_directory/something.rb
      invoke    test_unit
      remove      test/models/my_directory/something_test.rb
      remove      test/fixtures/my_directory/somethings.yml
      invoke  resource_route
       route    namespace :my_directory do
    resources :somethings
  end
      invoke  scaffold_controller
      remove    app/controllers/my_directory/somethings_controller.rb
      invoke    haml
      remove      app/views/my_directory/somethings
      remove      app/views/my_directory/somethings/index.html.haml
      remove      app/views/my_directory/somethings/edit.html.haml
      remove      app/views/my_directory/somethings/show.html.haml
      remove      app/views/my_directory/somethings/new.html.haml
      remove      app/views/my_directory/somethings/_form.html.haml
      invoke    test_unit
      remove      test/controllers/my_directory/somethings_controller_test.rb
      invoke    helper
      remove      app/helpers/my_directory/somethings_helper.rb
      invoke      test_unit
      invoke    jbuilder
      remove      app/views/my_directory/somethings
      remove      app/views/my_directory/somethings/index.json.jbuilder
      remove      app/views/my_directory/somethings/show.json.jbuilder
      remove      app/views/my_directory/somethings/_my_directory_something.json.jbuilder
      invoke  assets
      invoke    coffee
      remove      app/assets/javascripts/my_directory/somethings.coffee
      invoke    scss
      remove      app/assets/stylesheets/my_directory/somethings.scss
      invoke  scss

That generates some paths where the files should be, and try to delete that files if exist, don't mind if you create that files with scaffold or manually. But if that some files doesn't exist it only skip that files without advise in console output

In my app that files wasn't create in the correct directory so rails d scaffold can't remove it

Rails DB Migration - How To Drop a Table?

You won't always be able to simply generate the migration to already have the code you want. You can create an empty migration and then populate it with the code you need.

You can find information about how to accomplish different tasks in a migration here:

http://api.rubyonrails.org/classes/ActiveRecord/Migration.html

More specifically, you can see how to drop a table using the following approach:

drop_table :table_name

Removing a Devise user model possible?

I don't think devise offers a generator that would bring your model back to a previous version (similar to rails destroy migration ...). Apart from removing the devise method call from your model, you would need to get rid of the table itself (in a migration) and all the generated templates and controllers referring to the Student model, just to keep things clean.

Deleting empty asset files in Rails

rails generate scaffold is just a helper. It simply generated everything that could possibly be useful to you.

Sure you can delete all unneeded files. You could also delete a model or controller after it has been created if you don't need it anymore.

How do I Create a Rails Model from a Subset of Table Records

This is called Single Table Inheritance (STI).

If you had a column named type in your table, it would likely work automatically. But you can change this column name that Rails uses to tell types apart.

http://api.rubyonrails.org/classes/ActiveRecord/Base.html

Single table inheritance

Active Record allows inheritance by storing the name of the class in a column that by default is named “type” (can be changed by overwriting Base.inheritance_column). This means that an inheritance looking like this:

class Company < ActiveRecord::Base; end
class Firm < Company; end
class Client < Company; end
class PriorityClient < Client; end

When you do Firm.create(:name => "37signals"), this record will be saved in the companies table with type = “Firm”. You can then fetch this row again using Company.where(:name => '37signals').first and it will return a Firm object.

So, try this code

class Car < ActiveRecord::Base
  set_table_name 'Vehicle_Table'
  self.inheritance_column = :vehicle_type
end

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