A tiny concern for generating a UUID for a model. Code heavily based off Rails' `has_secure_token` method

model.rb

class Model < ActiveRecord::Base
  include UuidConcern
  
  # uuid attribute is `:uuid` by default. Optionally pass in attribute name, e.g `has_uuid :unique_token` 
  has_uuid 
end

uuid_concern.rb

module UuidConcern
  extend ActiveSupport::Concern

  included do
    def self.has_uuid(attribute: :uuid)
      # Load securerandom only when has_secure_token is used.
      require 'active_support/core_ext/securerandom'
      define_method("regenerate_#{attribute}") { update! attribute => self.class.generate_uuid }
      before_create { self.send("#{attribute}=", self.class.generate_uuid) unless self.send("#{attribute}?")}
    end

    private

    def self.generate_uuid
      SecureRandom.uuid
    end
  end
end