refactoring a Lund credit card checker

gistfile1.rb

# Original unrefactored code:
class CreditCard
  #initialize
  def initialize(card_number)
    raise ArgumentError.new("Card nunber must be 16 digits long") if card_number.to_s.length != 16
    @card_number = cardNumber
  end

  #convert a string card number to Luhn  Algorithm
  def luhnConvert(card_number)
    digits = (card_number).scan(/\d{1}/) #split card number to individual digits
    for i in 0..(card_number).length
      if !(i % 2 == 0) #for every number in a odd position
        digits[i] = (digits[i].to_i * 2).to_s #multiply numbers in odd address by 2
        if digits[i].to_i > 9 #if greater than 2 digits
          digits[i] = sumDigits(digits[i]).to_s #sum the digits
        end
      end
    end
    return digits #return an array of converted card_number as individual digits
  end

  #sum multi-digit number's digits from a string
  def sumDigits(num)
    sum = num.scan(/\d{1}/)
    return sum.inject(0) {|total, digit| total += digit.to_i }
  end

  #check card
  def check_card
    convertedNumber = luhnConvert(@card_number.to_s) #convert credit card number into Luhn Algorithm form
    mod10 = convertedNumber.inject(0) { |sum, d| sum += d.to_i  } #creates the sum of converted number for %10 test
    return mod10 % 10 == 0 ? true: false
  end
end


# Refactored code

class CreditCard
  def initialize(card_number)
    raise ArgumentError.new("Card number must be 16 digits long") if card_number.to_s.length != 16
    @card_number = card_number
  end

  def get_luhn_sum
    digits = @card_number.to_s.split('').map{|x| x.to_i}
    for i in 0..@card_number.to_s.length
      if i % 2 != 0
        doubled = digits[i] * 2
        digits[i] = (doubled <= 9 ? doubled : doubled - 9)
      end
    end
    digits.reduce(:+)
  end

  def check_card
    get_luhn_sum % 10 == 0
  end
end

# In the end, I changed the way we calculated the sum of 2 digit numbers between 10-20 (which allowed me to remove the sumDigits method), and I used underscore method names instead of camel case