Summarizing Rails naming conventions

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While writing Rails code we prefer convention over configuration and we follow the conventions adopted by Rails. Because of this we are not required to write a lot of configuration code.

The idea is that if you configure your applications in the same way most of the time then this can be treated as the default way of setting up a Rails application.

Rails has adopted a default way of doing things and laid down some conventions that should be followed while working with Rails. Naming conventions being one of the few conventions.

In this chapter we will be summarizing Rails naming conventions which we have used in our Granite application.

General naming conventions in Ruby

  • Class names and module names use PascalCase. For example, ApplicationController.

  • Method and variable names use snake_case. For example, attr_accessor.

Naming conventions in a Rails application are more or less based on the general naming conventions in Ruby language.

We will take a look at the naming conventions used in models, views and controllers of a Rails application as Rails is based on an MVC pattern and these three components serve as the core of any Rails application.

Naming conventions in Active Record model

Active Record uses some naming conventions to map models with database tables. Rails pluralizes the class names to find the respective database tables. For example, in our Granite application, for User class, we have the users table.

Rails is capable of pluralizing (and singularizing) both regular and irregular words. Model class names must use the CamelCase form when composed of two or more words, while the database table names must use the snake_case form.

For example, the UserNotification model class has the first letter of each word capitalized and its corresponding table name, user_notifications is plural with underscores separating the two words.

You can also override the naming convention using the ActiveRecord::Base.table_name= method to specify the table name that should be used instead of the table name Rails expects due to the naming conventions.

Since ApplicationRecord inherits from ActiveRecord::Base class, table_name= method is available to all models which inherit from ApplicationRecord.

For example, for the UserNotification class, we could have set the table name to notifications, like so:

1class UserNotification < ApplicationRecord
2  self.table_name = "notifications"

Naming model associations

Let's also understand how to name associations inside a model.

While declaring an association using methods like belongs_to and has_one, the association name must match with the singular form of associated model name because the aforementioned methods create an association between each instance of the declaring model with a single instance of the other model.

For example:

1class Task < ApplicationRecord
2  belongs_to :user

Had we used the pluralized form of user model in the above example and tried to create the instance using Task.create(users: @user), Rails would have thrown an exception for uninitialized constant Task::Users.

This is because Rails automatically infers the class name from the association name. If the association name is wrongly pluralized, then the inferred class will be wrongly pluralized too. In this case the inferred class is User.

For declaring an association between one instance of the declaring model and multiple instances of the other model, the association name must match with the plural form of the other model's name. For example:

1class User < ApplicationRecord
2  has_many :tasks

Naming conventions for databases

As we discussed in the previous section, table names in a database should be plural and use the snake_case form. Same goes for the column names.

Foreign keys should be named following the pattern singularized_table_name_id. These are the fields that Active Record will look for when you create associations between your models.

For example, inside the tasks table we had created a foreign key by the name of user_id because Task model shares a belongs_to association with the User model.

Naming conventions for Controllers

Since a Controller is a Ruby class, it follows the general convention of naming a Ruby class. It uses CamelCase and has the Controller keyword as a suffix.

There are two key details to note here:

  • The name of the controller is usually plural. For example, notice how tasks is plural in TasksController.

  • The Controller keyword suffix is always singular. Meaning we don't use Controllers as suffix.

Controller actions are methods and use snake_case. Their names usually match the route names defined in the routes config file.

In case of RESTful routes, controller actions are usually named after the standard CRUD operations performed by RESTful routes namely index, show, new, create, edit, update and delete. For example:

1resources :users, only: %i[create index]

All requests for creating a user on the users route will instantiate the UsersController model and call it's create action.

Naming conventions for routes

Route names use the snake_case form, and usually match the corresponding controller's name without the controller suffix.

Route names can be singular or plural depending upon the resource type. In Rails we have both singular as well as plural resources. We have already discussed the difference between them in one of the [early chapters](/learn-rubyonrails-book/restful-routes-in-ruby-on-rails#difference-between-singular resource-and resources-in-rails-routes) in the book.

However, both singular as well as plural resources map to a plural controller by default. For example:

1resources :users
2resource :comment

In the above example, requests on users and comment route will be routed to UsersController and CommentsController respectively. Note that even though comment is a singular resource, it is mapped to the CommentsController where comments is plural.

Naming conventions for Views

All of our view files need to reside in the appropriate view folders, which we must first create and name properly.

In our application, we have a view folder for each of the controllers. We use the following naming convention for our view folders.

The name of the folder within app/views should be the same as the associated controller name. And also folder names should be snake_case.

View files should match the corresponding action names and use snake_case followed by the appropriate response type and file extension in this particular order separated by a dot(.).

This is the format of the view file with the associated controllers view folder:


For example, in our Granite application we have stored all view files related to the TasksController inside app/views/tasks directory.

And view file corresponding to the show action of TasksController is app/views/tasks/show.json.jbuilder where show is the action name and json.jbuilder are response type and file extension respectively.

Naming conventions in services, workers and carriers

All services, workers and carriers should reside within app/services, app/workers and app/carriers directories respectively. Their file names should use snake_case and should be suffixed with _service, _worker and _carrier to clearly define their responsibilities.

Since services, workers and carriers are all classes, they should follow the general naming conventions of naming a class in Ruby i.e. their names should use CamelCase and match with their camelized file names.

For example, in the Granite application, TodoNotificationWorker class is present inside app/workers/todo_notification_worker.rb.

Naming conventions and folder structure for tests

In Rails, the tests that you write along with fixtures and other test-related files such as factories and test_helper, all goes inside the tests folder.

It is suggested that the tests directory structure should mirror the app directory's structure. This makes it easy to locate corresponding code and its test files.

Another important point to note is that the name of a test file should contain _test suffixed to the name of the corresponding file which is being tested.

For example, if TasksController in the Granite application was present inside the app/controllers/api/v1/tasks_controller.rb, then its corresponding test file should have been present inside tests/controllers/api/v1/tasks_controller_test.rb, which in turn mirrors the folder structure of the app directory.

tests folder also contains a subfolder for factories. Factory names and model names should have a one to one correspondence. For example, in Granite, task model and task factory are both named Task.rb

Let's also talk about naming test cases in Rails. Test cases are Ruby methods in a unit test class hence they should use snake_case.

Like all method names in Rails, test cases should have a descriptive and meaningful name for better readability. A good rule of thumb is to mention what is being tested and the constraints under which the test is being performed.

Let's look at this with the help of an example. Consider the test_not_found_error_rendered_for_invalid_task_slug test case in TasksControllerTest. It is pretty clear from the name itself that we are testing if a not_found error will be thrown if an invalid task slug is given. In this case, response is the entity that is being tested and invalid task slug is the constraint.

A test case name should always start with test_ for it to be executed while running the tests as discussed before in the Testing User model chapter

There is nothing to commit in this chapter as it's an in-depth chapter that doesn't have anything to do with our granite application.