uninitialized constant PackagesController::RiCal

I am getting error while trying to create ics file please review my code whats wrong with this:

uninitialized constant PackagesController::RiCal

Do I need to include or something else?

def i_cal
  pack = Administration::MerchantPackage.find(params[:id])
  loc = pack.offering.merchant.address.to_s + pack.offering.merchant.city.to_s
 cal = RiCal.Calendar do
   event do
     description pack.subtitle
     dtstart DateTime.parse(pack.start_date.strftime('%m/%d/%Y %H:%M:%S'))
     dtend DateTime.parse(pack.end_date.strftime('%m/%d/%Y %H:%M:%S'))
     location loc
     add_attendee current_user.email rescue ''
     alarm do
       description "Segment 51"
     end
   end
 end

When I try ::RiCal.Calendar it give me error:

uninitialized constant RiCal