Facebook signed_request + Rails (with Koala)

gistfile1.rb

class ApplicationController < ActionController::Base
  protect_from_forgery

  def fb_liked?
    session[:signed_request]['page']['liked'] if session[:signed_request]
  end

  def fb_admin?
    session[:signed_request]['page']['admin'] if session[:signed_request]
  end

  helper_method :fb_liked?, :fb_admin?

  before_filter do
    if params[:signed_request]
      oauth = Koala::Facebook::OAuth.new(ENV['FB_APP_ID'], ENV['FB_APP_SECRET'])
      session[:signed_request] = oauth.parse_signed_request(params[:signed_request])
    end
  end
end