Rails: prefixing the path of scoped routes
scope(:module => 'api', constraints: {subdomain: 'api'}, defaults: {format: 'json'}) do
  scope('1', module: 'v1') do
    resources :posts
  end
end

posts     GET    /1/posts(.:format)          api/v1/posts#index {:format=>"json"}
          POST   /1/posts(.:format)          api/v1/posts#create {:format=>"json"}
new_post  GET    /1/posts/new(.:format)      api/v1/posts#new {:format=>"json"}
edit_post GET    /1/posts/:id/edit(.:format) api/v1/posts#edit {:format=>"json"}
post      GET    /1/posts/:id(.:format)      api/v1/posts#show {:format=>"json"}
          PUT    /1/posts/:id(.:format)      api/v1/posts#update {:format=>"json"}
          DELETE /1/posts/:id(.:format)      api/v1/posts#destroy {:format=>"json"}

scope('1', module: 'v1', name_prefix: 'v1_')