Engine routes in Application Controller - ruby-on-rails-3

Question

I have a before_filter hook in my main app's application controller that does something like: (It doesn't just put a link in the flash, there is a message, but it isn't relevant to the question, it just accesses the route in the method)
class ApplicationController < ActionController::Base
before_filter :set_link
def set_link
flash[:notice] = items_path
end
end
This works fine for the app, however when I go into the controllers for an engine I made I get the exception
No route matches {:controller=>"items", :action=>"index"}
I understand that when in the engine, the routes helpers are for the engine unless prefixed with main_app
So changing the method in the application controller to
def set_link
flash[:notice] = main_app.items_path
end
Gets rid of the exception but I really don't want to have to do that. Is there another solution to getting the engine to recognize the main_app routes?
EDIT:
This also happens if the application layout calls path helpers. So if the engine is designed to integrated into the main_app's layout then this issue will crop there up too.

Answer 1

Mountable engines are designed to work like this, that is isolate the main app routes and the engine routes.
If you want the two sets of routes to be merged, you can use a non-isolated engine. The first step is removing the isolated_namespace method call in your engine definition:
module MyEngine
class Engine < Rails::Engine
isolate_namespace MyEngine # remove this line
end
end
The second step is to convert your routes in my_engine/config/routes.rb, you should go from this:
MyEngine::Engine.routes.draw do
# stuff that routes things
end
to this:
Rails.application.routes.draw do
# stuff that routes things
end
and remove the mount method call in your application's routes:
App::Application.routes.draw do
mount MyEngine::Engine => "/engine" # remove this line
end
The main advantages of doing it this way would be:
No need to monkey-patch rails. I know devise does this, but this could be a leftover from the days when engines didn't exist in rails.
No need to mount the engine in the application routes. On the other hand, this could backfire if you'd like to control more precisely the insertion point as all you engine routes would be called after (or before, I don't have the answer to this question) your main routes.
If you're looking for documentation on engines, the rails docs for the Engine class are a pretty good starting point. I'd strongly recommend that you read them (in case you haven't yet) if you're interested in the subject.

Answer 2

I figured out how to do this. The problems lies within the isolated namespace. In order to integrate the engine with the app and share the same layout (which may have path helpers from the main app) I did this:
Firstly I removed config/routes.rb from the engine
Then I removed the isolate_namespace from the engine class
module MyEngine
class Engine < Rails::Engine
- isolate_namespace MyEngine
end
end
end
I added a file that was loaded in the engine:
module ActionDispatch::Routing
class Mapper
def mount_my_engine_at(mount_location)
scope mount_location do
#Declare all your routes here
end
end
end
end
Finally, in the main app's config/routes.rb instead of 'mount'ing the engine, you can call your method
mount_my_engine_at "mount_location"
This will basically 'mount' your engine as part of the main app instead of being isolated from it. It is similar to how Devise does it too.

Answer 3

You can keep the isolate_namespace.
In your engine routes.rb
MyEngine::Engine.routes.draw do
...
root to: "something#index"
end
Rails.application.routes.draw do
get "something", to: "my_engine/something#index"
end
And then in the main app routes.rb
Rails.application.routes.draw do
mount MyEngine::Engine => "/anything_you_want"
root to: "main#index"
end
This way you can choose what routes you want to expose (and which you do not)

Answer 4

You can keep the isolate_namespace, as strongly recommended by Rails Engine guide, and do this:
# inside your main_app's config/routes.rb
Rails.application.routes.draw do
root to: 'home#index'
mount MyEngine::Engine, at: "/"
end
# inside your engine's controller
module MyEngine
class SomeController << ::ApplicationController
# include main_app's route helpers
helper Rails.application.routes.url_helpers
end
end
And inside your gem, make sure all the url helpers are prefixed with the correct routing proxy method (e.g. my_engine.pages_path).
Your main_app's layout and engine's controller will route and link to those url helpers correctly to the main app. You don't have to add "main_app" prefix anywhere to the main app. The only downside is you're mounting your engine's routes at main_app's root path, which could collide with any routes by the same name. This is expected anyway if you were to do non-isolate_namespace.

Answer 5

The easiest way is to draw the routes in both the main app, and the engine, so that they are accessible to both:
[MyEngine::Engine, App::Application].each do |app|
app.routes.draw do
# Declare all your routes here
end
end