Referrable Rails

referrable.rb

module Referrable
  extend ActiveSupport: :Concern
  
  included do
    has_one referral, foreign_key: "referred_user_id", dependent: : destroy has_one referring_user, through: :referral alias_method :referred_by, :referring_user
    has_many :referrals, foreign_key: "referring_user_id", dependent: :nullify has_many :referred_users, through: referrals
    validates :referral_code, uniqueness: true, allow_nil: true
  end
end

user.rb

class User < ApplicationRecord
  include Referrable
end

__END__

user.referred_by
user.referred_users