How can I make routes from a Rails 3 engine available to the host application?

Question

I have a Rails 3 application with several engines containing additional functionality. Each engine is a separate service that customers can purchase access to.

I am, however, having a problem with routes from the engines that aren't readily available to the controllers and views.

controller:

class ClassroomsController < ApplicationController   ..   respond_to :html    def index     respond_with(@classrooms = @company.classrooms.all)   end    def new      respond_with(@classroom = @company.classrooms.build)   end    .. end 

app/views/classrooms/new.html.haml:

= form_for @classroom do |f|   ..   f.submit 

config/routes.rb in engine:

MyEngineName::Engine.routes.draw do   resources :classrooms end 

config/routes.rb in app:

Seabed::Application.routes.draw do   mount MyEngineName::Engine => '/engine'   ... end 

lib/my_engine_name.rb in engine:

module MyEngineName   class Engine < ::Rails::Engine   end end 

attempting to go to /classrooms/new results in

NoMethodError in Classrooms#new  Showing app/views/classrooms/_form.html.haml where line #1 raised:   undefined method `hash_for_classrooms_path' for #<Module:0x00000104cff0f8> 

and attempting to call classrooms_path from any other view results in the same error. I can, however, call MyEngineName::Engine.routes.url_helpers.classrooms_path and get it working. I'm thinking I might have defined the routes wrong, but can't find another way that works.

Tried running the app with both Passenger (standalone and Apache module) and WEBrick (rails server). Using latest Rails from Git (7c920631ec3b314cfaa3a60d265de40cba3e8135).

Answer 1

I had the same problem, and found this in the documentation:

Since you can now mount an engine inside application’s routes, you do not have direct access to Engine‘s url_helpers inside Application. When you mount an engine in an application’s routes, a special helper is created to allow you to do that. Consider such a scenario:

# config/routes.rb MyApplication::Application.routes.draw do   mount MyEngine::Engine => "/my_engine", :as => "my_engine"   get "/foo" => "foo#index" end 

Now, you can use the my_engine helper inside your application:

class FooController < ApplicationController   def index     my_engine.root_url #=> /my_engine/   end end