Rails routes file can become lengthy if the application becomes huge. It can be difficult to manage routes especially if we have multiple namespace and route action names are similar across namespaces. Splitting Rails routes helps us manage routes easily in an application.

Rails routes file is available at config/routes.rb by default. It generally follows the pattern given below.

Rails.application.routes.draw do
  # route 1
  # route 2
  # route .
  # route .
  # route N
end

As we can see, Rails.application.routes calls method draw by passing a block of routes defined in this file. Rails.application.routes is an instance of ActionDispatch::Routing::RouteSet.

Let’s take an example config/routes.rb file with some routes.

# config/routes.rb

Rails.application.routes.draw do
  namespace :admin do
  # ..
  end

  namespace :customer do
  # ..
  end

  namespace :third_party do
  # ..
  end
end

To split this routes.rb file into multiple files:

1. Create a directory config/routes.

mkdir -p config/routes

2. Create new files in the config/routes directory. In this case, admin_routes.rb, customer_routes.rb, third_party_routes.rb

# config/routes/admin_routes.rb
module AdminRoutes
  def self.extended(router)
    router.instance_exec do

      # put admin namespace routes here
      namespace :admin do
        # ..
      end

    end
  end
end

Similarly, define customer_routes.rb and third_party_routes.rb files.

# config/routes/customer_routes.rb
module CustomerRoutes
  def self.extended(router)
    router.instance_exec do

      # put customer namespace routes here
      namespace :customer do
        # ..
      end

    end
  end
end

# config/routes/third_party_routes.rb
module ThirdPartyRoutes
  def self.extended(router)
    router.instance_exec do

      # put third_party namespace routes here
      namespace :third_party do
        # ..
      end

    end
  end
end

Make sure these newly created route files are auto loaded. Add config/routes directory files in autoload paths in config/application.rb

config.autoload_paths += Dir[ Rails.root.join(Rails.root.join('config', 'routes', '**/') ]

This auto loads modules defined in config/routes directory and can be used in config/routes.rb file. Let’s load these routes in config/routes.rb file as given below.

Rails.application.routes.draw do
  extend AdminRoutes
  extend CustomerRoutes
  extend ThirdPartyRoutes
end

Run the rails application to verify that routes splitted in multiple files are loaded correctly and they work as expected.