Inspired after reading about Luhn Algorithm (or Modulus 10 Algorithm) article (https://en.wikipedia.org/wiki/Luhn_algorithm) from Wiki, I made this gem to easily validate a variety of identification numbers, for example Social Insurance numbers, or Credit card numbers.

Add this line to your application's Gemfile:

gem 'luhn_algorithm'

And then execute:

$ bundle 

Or install it yourself as:

$ gem install luhn_algorithm 

class Member include ActiveModel::Model attr_accessor :social_insurance_number validates_luhn_algorithm_of :social_insurance_number end 

OR

class Member include ActiveModel::Model attr_accessor :social_insurance_number validates :social_insurance_number, luhn_algorithm: true end 

person = Member.new(social_insurance_number: 'a valid number') person.valid? # => true 

You can also pass in a customized message when validating an attribute with Luhn Algorithm, for example

validates_luhn_algorithm_of :social_insurance_number, message: 'is not in the correct format' 

If you want to validate a number with Luhn algorithm on console, you can just type LuhnAlgorithm.valid?(<your_number_here>), for example:

require 'luhn_algorithm' LuhnAlgorithm.valid?(4111111111111111) 

Bug reports and pull requests are welcome on GitHub at https://github.com/thukim/luhn_algorithm. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

The gem is available as open source under the terms of the MIT License.

Everyone interacting in the LuhnAlgorithm project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.