foo.rb

    
module OrderPlacementService

    def fetch_user_billing_info(params)
     HashParamsChecker.check_params(
          {:inputs => { :pre_user_id => 13 }
          },
          params
      )
      #...
    end

    def fetch_notification_email(params)
      HashParamsChecker.check_params(
          {
            :inputs => { :pre_user_id => 13 },
            :fetch_user_billing_info => {:user_billing_info => "usi object"}
          },
          params
      )
      #...
    end   
end



class OrderPlacer
  @@user

   def initialize(id)
     @user = User.find_by_id(id)
   end

   def fetch_user_billing_info(params)
    @user.stuff
      #...
    end

    def fetch_notification_email(params)
      @user.stuff
      #...
    end
end