Rails use the same naming convention as Ruby with some additions:
Link the Ruby Naming Convention post

Files, Directories and other pluralization
Files are named using lowercase and underscores. Assuming we have an Users controller then the following other conventions will apply:

  • That there is a helper module named UsersHelper in the users_helper.rb found in the app/helpers directory.
  • Rails will look for view template files for the controller in the app/views/users directory.
  • Output from this view will then be used in the layout defined in the users.html.erb in the app/views/layouts directory.
  • Test files including user_test.rb will be created in the /test/unit directory, a file will be created in the /test/fixtures directory called users.yml and finally a file called users_controller_test.rb will be created in the /test/functional directory

Variables - i.e. user_status, total
Variables are named where all letters are lowercase and words are separated by underscores.

Class and Module - i.e. UserPermissions
Classes and modules use MixedCase and have no underscores, each word starts with a uppercase letter.

Controller - i.e. UsersController
Controller class names are pluralized, such that UsersController would be the controller class for the users table. Rails will then look for the class definition in a file called users_controller.rb in the /app/controllers directory.

Model - i.e. User
The model is named using the class naming convention of unbroken MixedCase and is always the singular of the table name.
For example:

  • Table name might be users (plural)
  • The model name would be User (singular)
  • Rails will then look for the class definition in a file called user.rb in the /app/models directory.
  • If the model class name has multiple capitalised words, the table name is assumed to have underscores between these words.

Database Table - e.g. user_permissions, users
Table names have all lowercase letters and underscores between words, also all table names need to be plural.

Primary Key
The primary key of a table is assumed to be named id.

Foreign Key
The foreign key is named with the singular version of the target table name with _id appended to it, e.g. order_id in the items table where we have items linked to the orders table.

Many to Many Link Tables
Tables used to join two tables in a many to many relationship is named using the table names they link, with the table names in alphabetical order, for example categories_users.

Automated Record Timestamps
You can get ActiveRecord to automatically update the create and update times of records in a database table. To do this create two specially named columns created_at and updated_at to your table, i.e. t.datetime :created_at and t.datetime :updated_at. If you only want to store the date rather than a date and time, use :created_on and :updated_on.

Naming Convention Summary

Model Naming Convention

Table: 		users
Class: 		User
File: 		/app/models/user.rb
Primary Key: 	id
Foreign Key: 	client_id
Link Tables: 	products_users

Controller Naming Convention

Class: 		UsersController
File: 		/app/controllers/users_controller.rb
Layout: 	/app/layouts/users.html.erb

View Naming Convention

Helper: 	/app/helpers/users_helper.rb
Helper Module:  UsersHelper
Views: 		/app/views/users/… (index.html.erb for example)

Tests Naming Convention

Unit: 		/test/unit/user_test.rb
Functional: 	/test/functional/users_controller_test.rb
Fixtures: 	/test/fixtures/users.yml