facebooker_multi_app.rb

# config/initializers/facebooker.rb
module Facebooker
  class << self
    def fetch_config_for(api_key)
      if app = Application.find_by_api_key(api_key)
        {
          'api_key'                         => app.api_key,
          'secret_key'                      => app.secret,
          'canvas_page_name'                => app.canvas_name,
          'callback_url'                    => app.callback_url,
          'set_asset_host_to_callback_url'  => true
        }
      else
        nil
      end
    end
  end
end