Render engine within application layout

I have successfully used layouts of my parent application in my engines. Firstly, based on Section 4.3.2 of the Rails Guides (Engines), in order to access the parent applications ApplicationController’s variables (like session, as you’re using above), you need to replace the engine’s application_controller.rb from this that you currently have:

module Module1
  class ApplicationController < ActionController::Base
    layout "core"
  end
end

to this:

class Module1::ApplicationController < ::ApplicationController
end

This will inherit the parent application’s ApplicationController, along with all it’s variables.

Secondly, you’ll need to delete the file app/views/layouts/application.html.erb from your engine views, as it will not be needed since you’re using the parent application’s one.

Now when you render a view of Module1 from the parent application, the layout of the parent application will be used, and all the session[] variables will be evaluated correctly.

Do not forget to add the words “main_app.” before each link in your layouts, otherwise it will try and look for the paths in the engine instead of the parent application. For example, if the layout in the parent application includes a link to some_path (that is a view in the parent application), when showing a view in the engine that uses this layout will try and look for some_path in the Engine instead of the parent application. You will need to change the link to main_app.some_path for it to work.

Hope this helps.