How to Use Namespace in Routes in Ruby on Rails

In Ruby on Rails, use namespace in your config/routes.rb file to group related routes under a common URL prefix and controller module. This helps organize controllers and URLs, for example, namespace :admin do creates routes like /admin/products handled by Admin::ProductsController.

Syntax

The namespace method wraps routes inside a URL path prefix and a controller module. The syntax is:

• namespace :name do ... end: groups routes under /name URL prefix.
• Controllers must be inside a module named after the namespace, e.g., Name::ControllerName.
• Routes inside the block inherit the namespace path and controller scope.

ruby

Rails.application.routes.draw do
  namespace :admin do
    resources :products
  end
end

Example

This example shows how to create an admin namespace for product management. It generates URLs prefixed with /admin and expects controllers inside the Admin module.

ruby

Rails.application.routes.draw do
  namespace :admin do
    resources :products
  end
end

# Controller: app/controllers/admin/products_controller.rb
module Admin
  class ProductsController < ApplicationController
    def index
      render plain: "Admin Products Index"
    end
  end
end

Output

Visiting /admin/products shows "Admin Products Index"

Common Pitfalls

Common mistakes include:

• Not placing controllers inside the correct module folder (e.g., app/controllers/admin/ for Admin namespace).
• Using scope instead of namespace when you want module scoping.
• Forgetting that namespace adds both URL prefix and controller module, so controller names must match.

ruby

Rails.application.routes.draw do
  # Wrong: controller not in Admin module
  namespace :admin do
    get 'dashboard', to: 'dashboard#index'
  end
end

# Controller placed at app/controllers/dashboard_controller.rb (WRONG)
class DashboardController < ApplicationController
  def index
    render plain: "Dashboard"
  end
end

# Correct controller placement:
module Admin
  class DashboardController < ApplicationController
    def index
      render plain: "Admin Dashboard"
    end
  end
end

Quick Reference

Concept	Description	Example
namespace	Groups routes under URL prefix and controller module	namespace :admin do ... end
URL prefix	Added automatically from namespace name	/admin/products
Controller module	Controllers must be inside matching module	Admin::ProductsController
resources	Defines RESTful routes inside namespace	resources :products
scope vs namespace	scope only adds URL prefix, namespace adds module too	scope :admin do ... end vs namespace :admin do ... end

Key Takeaways

Use namespace in routes to group URLs and controllers under a common module and path.

Controllers must be placed inside a folder and module matching the namespace name.

Namespace adds both URL prefix and controller module scope automatically.

Common errors include mismatched controller modules or using scope when namespace is needed.

Use resources inside namespaces to create RESTful routes with proper URL and controller structure.