Service Objects

Controller before SO

 class TripReservationsController < ApplicationController
   def create
     reservation = TripReservation.new(params[:trip_reservation])
     trip = Trip.find_by_id(reservation.trip_id)
     agency = trip.agency

     payment_adapter = PaymentAdapter.new(buyer: current_user)

     unless current_user.can_book_from?(agency)
       redirect_to trip_reservations_page, notice: TripReservationNotice.new(:agency_rejection)
     end

     unless trip.has_free_tickets?
       redirect_to trip_reservations_page, notice: TripReservationNotice.new(:tickets_sold)
     end

     begin
       receipt = payment_adapter.pay(trip.price)
       reservation.receipt_id = receipt.uuid

       unless reservation.save
         logger.info "Failed to save reservation: #{reservation.errors.inspect}"
         redirect_to trip_reservations_page, notice: TripReservationNotice.new(:save_failed)
       end

       redirect_to trip_reservations_page(reservation), notice: :reservation_booked
     rescue PaymentError => e
       logger.info "#{current_user.name} failed to pay for #{trip.name}: #{e.message}"
       redirect_to trip_reservations_page, notice: TripReservationNotice.new(:payment_failed, reason: e.message )
     end
   end
 end

Controller with SO

class TripReservationsController < ApplicationController
  def create
    user = current_user
    trip = Trip.find_by_id(reservation.trip_id)
    agency = trip.agency
    reservation = TripReservation.new(params[:trip_reservation])

    begin
      trip_reservation_service.process(user, trip, agency, reservation)
      redirect_to trip_reservations_page(reservation), notice: :reservation_booked
    rescue TripReservationService::TripPaymentError => e
     redirect_to trip_reservations_page, notice: TripReservationNotice.new(:payment_failed, reason: e.message)
   rescue TripReservationService::ReservationError
     redirect_to trip_reservations_page, notice: TripReservationNotice.new(:save_failed)
   rescue TripReservationService::NoTicketError
     redirect_to trip_reservations_page, notice: TripReservationNotice.new(:tickets_sold)
   rescue TripReservationService::AgencyRejectionError
     redirect_to trip_reservations_page, notice: TripReservationNotice.new(:agency_rejection)
   end
 end

 private

 def trip_reservation_service
   TripReservationService.new( PaymentAdapter(buyer: current_user), logger )
 end
end

SO

 class TripReservationService
   class TripPaymentError < StandardError; end
   class ReservationError < StandardError; end
   class NoTicketError < StandardError; end
   class AgencyRejectionError < StandardError; end

   attr_reader :payment_adapter, :logger

   def initialize(payment_adapter, logger)
     @payment_adapter = payment_adapter
     @logger = logger
   end

   def process(user, trip, agency, reservation)
     raise AgencyRejectionError.new unless user.can_book_from?(agency)
     raise NoTicketError.new unless trip.has_free_tickets?

     begin
       receipt = payment_adapter.pay(trip.price)
       reservation.receipt_id = receipt.uuid

       unless reservation.save
         logger.info "Failed to save reservation: #{reservation.errors.inspect}"
         raise ReservationError.new
       end
     rescue PaymentError => e
       logger.info "#{user.name} failed to pay for #{trip.name}: #{e.message}"
       raise TripPaymentError.new e.message
     end
   end
 end