Luhn Validator

Luhn.rb

class Luhn
  def self.valid?(string)
    transformed = string.gsub(/ /,'') #Remove spaces
    return false if transformed.length < 1 #Return false if length less than 1
    return false if transformed.match?(/\D/) #Return false if any non digit characters
    # Reverse the string Scan for 2 capture groups
    transformed = transformed.reverse.scan(/(.)(.)/).each do |pair|
      # Turn both items into integers
      pair[0] = pair[0].to_i
      pair[1] = pair[1].to_i
      # Double the last item
      transform = pair[1] * 2
      # If the doubled result is greater than 9 subtract 9
      pair[1] = transform > 9 ? transform - 9 : transform
    end
    # Flatten out the array, sum the items and check if its divisibleb by 10
    transformed.flatten.inject(:+)%10 == 0
  end
end