如何将 rails3 路由转换为 rails4

How to convert rails3 routes into rails4

我有以下 rails3 路线,我想将其转换为 rails4。

map.with_options(:conditions => {:subdomain => AppConfig['admin_subdomain']}) do |subdom|
  subdom.root :controller => 'subscription_admin/subscriptions', :action => 'index'
  subdom.with_options(:namespace => 'subscription_admin/', :name_prefix => 'admin_', :path_prefix => nil) do |admin|
    ...
  end
end
namespace :admin do
  constraints subdomain: AppConfig['admin_subdomain'] do
    root to: 'subscription_admin/subscriptions#index'
    namespace :subscription_admin do
      resources :some_resources
        # RESTful routes
      end
    end
  end
end

More info about constrains.