Checking a Credit Card Checksum : Utility Regexps « Development « Ruby

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Ruby » Development » Utility Regexps 
Checking a Credit Card Checksum


module CreditCard
  def creditcard?
    numbers = self.to_s.gsub(/[^\d]+/, '').split(//)

    checksum = 0
    0.upto numbers.length do |i|
      weight = numbers[-1*(i+2)].to_i * ((i%2))
      checksum += weight % 9
    end

    return numbers[-1].to_i == 10 - checksum % 10
  end
end

class String
  include CreditCard
end

class Integer
  include CreditCard
end


puts '1111 1111 6542 1319'.creditcard?                  
puts '1111111111111313'.creditcard?                     

 
Related examples in the same category
1.Validate an email address
2.Validate an email address with Resolv::DNS
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