FBGraph on facebook fan page with Ruby on Rails 3

I have many doubts with fbgraph ruby gem. I understand if my page is a independent application which can connect to Facebook.

Now I don´t unde开发者_如何学Pythonrstand how I should take the user information if my page is on Facebook fan page. I know what Facebook send me params['signed_request'].

However I don't understand how and when I should use fbgraph ruby wrapper if my site is on Facebook fan page.

I add a filter in my application controller.

def parse_facebook
 @auth = FbGraph::Auth.new(configatron.fb_authentication_app_key, configatron.fb_authentication_app_secret).from_signed_request params[:signed_request]
end

This could be modified for other scenarios however this is the simplest example.