When to use a singular router resource vs. a plural one

At the routing level, there are two methods that can be used to declare the routes: singular and plural.

Routes are generally defined as plural using the plural resources.

Singular routes* are a little different – they are written as singular resource.

Declaring a resource or resources generally corresponds to generating many default routes.

For example:

resources :profiles
  resource :profile

resource is singular. resources is plural.

When do we use Singular?

Plural resources are most commonly used. So, to understand singular resources think of this example: You are designing a social media platform. As a Facebook or LinkedIn user, if you click on your profile, you want the application to show your own profile. This is a common scenario that you can solve using singular resources.

We can define the profiles of users in our database, but we only need to view the profile so, therefore, we do not need all the other routes. Hence, we just generate the show route:

resources: profiles, only: show

Sometimes, you have a resource that clients always look up without referencing an ID. For example, you would like /profile to always show the profile of the currently logged in user.

A user can add a simple declaration with:

resource :profile, only: :show

This creates a route for a single profile and is done without changing any controller code. Now, the users have been enabled to access each other’s profiles.

resources :profiles, only: :show do
  resource :profile, only: :show
end

Because you might want to use the same controller for a singular route (/account) and a plural route (/accounts/45), singular resources map to plural controllers. This is so, for example, resource :photo and resources :photos will create both singular and plural routes that map to the same controller (PhotosController).

This implementation is called plural to singular route. It creates a profiles_profile route for a user to access the profiles of other users.