Namespace vs Scope in Rails Router

Difference and Similarity in the use cases between Namespace and Scope in Rails Router

When it comes to customization to Rails routes, some options like namespace and scope pops up which also has a lot of use case and importance in Rails application. It’s very common to forget about the difference between the two terms ‘namespace’ and ‘scope’, so let’s look into the working for each of the terms in this section.

Namespace

Starting with the simple topic among the two as :namespace. So basically :namespace changes (prefix name with) URL along with controller directory structure.

config/routes.rb
Rails.application.routes.draw do
  namespace :api, defaults: { format: :json } do
    resources :homes
  end
end

Then the routes available will be given as,

terminal=>
$ rake routes | grep homes
Prefix     Verb    URI Pattern               Controller#Action
api_homes  GET     /api/homes(.:format)      api/homes#index {:format=>:json}
           POST    /api/homes(.:format)      api/homes#create {:format=>:json}
api_home   GET     /api/homes/:id(.:format)  api/homes#show {:format=>:json}
           PATCH   /api/homes/:id(.:format)  api/homes#update {:format=>:json}
           PUT     /api/homes/:id(.:format)  api/homes#update {:format=>:json}
           DELETE /api/homes/:id(.:format)   api/homes#destroy {:format=>:json}

So the Prefix name got a prepend ‘api’, URL has a prepend /api and even the controller structure needs to get modified as,

app/controllers/api/homes_controller.rb
module Api
  class HomesController < ApplicationController
    # GET /api/homes
    def index
    end
  end
end

Scope

Similar to the :namespace, the :scope has few options which can control the changes in URL path, controller structure and Prefix path. Scope provides few options of :path, :as and :module. Generally the scope can be given as follows,

config/routes.rb
Rails.application.routes.draw do
  scope :api do
    resources :homes
  end
end

This will make available routes to change only the URL path (URI pattern) with prepend ‘/api’ as below,

terminal=>
$ rake routes | grep homes
Prefix Verb   URI Pattern              Controller#Action
homes  GET    /api/homes(.:format)     homes#index
       POST   /api/homes(.:format)     homes#create
home   GET    /api/homes/:id(.:format) homes#show
       PATCH  /api/homes/:id(.:format) homes#update
       PUT    /api/homes/:id(.:format) homes#update
       DELETE /api/homes/:id(.:format) homes#destroy

Scope with :module

The scope with the :module will change only the controller structure as below,

config/routes.rb
Rails.application.routes.draw do
  scope module: ‘api’ do
    resources :homes
  end
end

The available routes will be as follows,

terminal=>
$ rake routes | grep homes
Prefix   Verb    URI Pattern         Controller#Action
homes    GET    /homes(.:format)     api/homes#index
         POST   /homes(.:format)     api/homes#create
home     GET    /homes/:id(.:format) api/homes#show
         PATCH  /homes/:id(.:format) api/homes#update
         PUT    /homes/:id(.:format) api/homes#update
         DELETE /homes/:id(.:format) api/homes#destroy

Scope with :path

The scope with the :path will change only the URL path (URI Pattern) as below,

config/routes.rb
Rails.application.routes.draw do
  scope module: ‘api’, path: ‘api’ do
    resources :homes
  end
end

The available routes will be as follows,

terminal=>
$ rake routes | grep homes
CPrefix   Verb   URI Pattern              Controller#Action
homes    GET    /api/homes(.:format)     api/homes#index
         POST   /api/homes(.:format)     api/homes#create
home     GET    /api/homes/:id(.:format) api/homes#show
         PATCH  /api/homes/:id(.:format) api/homes#update
         PUT    /api/homes/:id(.:format) api/homes#update
         DELETE /api/homes/:id(.:format) api/homes#destroy

Scope with :as

The scope with the :as will change only the Prefix as below,

config/routes.rb
Rails.application.routes.draw do
  scope module: ‘api’, path: ‘api’, as: ‘api’ do
    resources :homes
  end
end

The available routes will be as follows,

terminal=>
$ rake routes | grep homes
Prefix     Verb      URI Pattern            Controller#Action
api_homes  GET      /api/homes(.:format)    api/homes#index
           POST     /api/homes(.:format)    api/homes#create
api_home   GET     /api/homes/:id(.:format) api/homes#show
           PATCH   /api/homes/:id(.:format) api/homes#update
           PUT     /api/homes/:id(.:format) api/homes#update
           DELETE  /api/homes/:id(.:format) api/homes#destroy

As shown in this last example, well it’s similar to namespace as it uses all the options available to scope, the change is just that prepend name in different options can have different values in scope.