Generating unique, hard-to-guess “coupon” codes

Question

My Rails app needs to generate electronic coupons for users. Each coupon given should have a unique coupon code that can be redeemed on our system.

For example a cou

Answer 1

Go with something like:

class Coupon < ActiveRecord::Base
  before_save generate_token

  validates_uniqueness_of :token

  def generate_token
    self.token = "#{current_user.id}#{SecureRandom.urlsafe_base64(3)}"
  end

end

EDIT: Here is a better answer