At the routing level, there are two methods that can be used to declare them: and resource. The former is for plural resources, the latter for singular ones.

Declaring a resource means to generate several default routes with just one line of code.

It generates:

Remove Routes

resources :books, only: [:new, :create, :show]
# equivalent to
resources :books, except: [:index, :edit, :update, :destroy]

Add Routes

Alongside with default routes we can specify extra routes for single (member) or multiple (collection) resources.

  member do
    # Generates /books/1/toggle, maps to Books::Toggle, named :toggle_book
    get 'toggle'
  end
  collection do
    get 'search'
  end
end

Imagine we have a controller named manuscripts, where we have actions like Manuscripts::Index, but we still want to expose those resources as /books. Using the :controller option will save our day.

resources :books, controller: 'manuscripts'
# GET /books/1 will route to Manuscripts::Show, etc.

It generates:

Remove Routes

resource :account, only: [:show, :edit, :update, :destroy]
# equivalent to
resource :account, except: [:new, :create]

Add Routes

  member do
    get 'avatar'
  end
  collection do
    # Generates /account/authorizations, maps to Account::Authorizations, named :authorizations_account
    get 'authorizations'
  end
end

resource :account, controller: 'customer'

Plural to plural

It generates default routes for books and the following ones.

Plural to singular

resources :books do
  resource :cover
end

It generates default routes for books and the following ones.

resource :account do
  resources :api_keys
end

It generates default routes for account and the following ones.

Singular To Singular

resource :account do