Old code that was hard to read and NOT polite

polite_remittance_slip.rb

module DEFT
  class RemittanceSlip

    def initialize(*credits)
      @credits = credits
    end

    def print
      output = print_header_record

      output << print_detail_records_for_credits

      output << print_detail_record_for_deposit

      output << print_trailer_record
    end

    private

    def print_header_record
      "0                 01MBL       RENTINGSMART PTY LTD      123456RENT PAYMENT#{Date.tomorrow.strftime("%d%m%y")}                                        \n"
    end

    def print_detail_records_for_credits
      output = ""

      @credits.each do |credit|
        output << print_detail_record_for(credit)
      end

      output
    end

    def print_detail_record_for(credit)
      "1#{credit.bsb_number}#{credit.account_number.rjust(9)} 50#{format_amount(credit.amount)}#{credit.payer_full_name.ljust(32)}RENT PAYMENT      123-456303103352RENTINGSMART LTD00000000\n"
    end

    def print_detail_record_for_deposit
      "1123-456303103352 13#{format_amount(@credits.sum(&:amount))}RENTINGSMART PTY LTD            LANDLORD PAYMENTS 123-456303103352RENTINGSMART LTD00000000\n"
    end

    def print_trailer_record
      "7999-999            0000000000#{format_amount(@credits.sum(&:amount))}#{format_amount(@credits.sum(&:amount))}                        #{number_of_detail_records}                                       #
    end

    def format_amount(amount)
      "%010d" % (amount*100).to_i
    end

    def number_of_detail_records
      "%06d" % (@credits.size + 1)
    end
  end
end

remitttance_slip.rb

module DEFT
  class RemittanceSlip

    def initialize(*credits)
      @credits = credits
    end

    def print
      output = ""

      output << "0                 01MBL       RENTINGSMART PTY LTD      123456RENT PAYMENT#{Date.tomorrow.strftime("%d%m%y")}                                        \n"

      @credits.each do |credit|
        output << "1#{credit.bsb_number}#{credit.account_number.rjust(9)} 50#{format_amount(credit.amount)}#{credit.payer_full_name.ljust(32)}RENT PAYMENT      123-456303103352RENTINGSMART LTD00000000\n"
      end

      output << "1123-456303103352 13#{format_amount(@credits.sum(&:amount))}RENTINGSMART PTY LTD            LANDLORD PAYMENTS 123-456303103352RENTINGSMART LTD00000000\n"

      output << "7999-999            0000000000#{format_amount(@credits.sum(&:amount))}#{format_amount(@credits.sum(&:amount))}                        #{number_of_detail_records}                             #

      output
    end

    def print_header_record

    end

    private

    def format_amount(amount)
      "%010d" % (amount*100).to_i
    end

    def number_of_detail_records
      "%06d" % (@credits.size + 1)
    end
  end
end