Last Updated: September 27, 2021

Use UUID keys in Active Record

Identify and associate your ActiveRecord models using validated UUID's.

gem 'uuid'
gem 'activesupport'
gem 'activerecord'
gem 'sqlite3'

require 'active_support'
require 'active_record'
require 'uuid'

ActiveRecord::Base.establish_connection adapter: "sqlite3", database: ":memory:";

ActiveRecord::Schema.define do
 self.verbose = false

 create_table :posts, id: false, primary_key: :uuid do |t|
 t.string :uuid, primary_key: true
 t.string :title
 t.text :content
 t.timestamps
 end
 add_index :posts, :uuid

 create_table :comments, id: false, primary_key: :uuid do |t|
 t.string :uuid, primary_key: true
 t.string :post_uuid
 t.text :content
 t.timestamps
 end
 add_index :comments, :uuid
 add_index :comments, :post_uuid
end

ActiveRecord::Reflection::AssociationReflection.class_eval do
 alias_method :derive_foreign_key_before_uses_uuids, :derive_foreign_key
 def derive_foreign_key
 key = derive_foreign_key_before_uses_uuids
 active_record.respond_to?(:uses_uuids?) && active_record.uses_uuids? ? key.sub(/_id$/, '_uuid') : key
 end
end

class UuidValidator < ActiveModel::EachValidator
 def validate_each(record, attribute, value)
 Uuid.new(value).valid_uuid? or
 record.errors[attribute] << (options[:message] || "is not a valid UUID")
 end
end

class Uuid
 attr_reader :value

 def self.build(uuid)
 uuid.is_a?(Uuid) ? uuid : new(uuid)
 end

 def self.generate
 new(UUID.new.generate)
 end

 def initialize(value)
 @value = value.to_s
 end

 def valid_uuid?
 @value =~ /\A[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}\z/
 end

 alias_method :to_s, :value
end

module UsesUuids
 extend ActiveSupport::Concern

 module SetsAfterInitialize
 extend ActiveSupport::Concern
 included do
 after_initialize :set_uuid
 end
 end

 module ActiveRecord
 extend ActiveSupport::Concern

 included do
 validates_uniqueness_of :uuid
 end

 def write_attribute(attr_name, value)
 _value = value.is_a?(Uuid) ? value.to_s : value
 super(attr_name, _value)
 end

 def read_attribute_for_validation(key)
 value = super
 value.is_a?(Uuid) ? value.to_s : value
 end

 module ClassMethods
 def primary_key
 :uuid
 end

 def uses_uuids?
 true
 end
 end

 end

 included do
 validates :uuid, presence: true, uuid: true
 end

 def uuid
 return nil unless self[:uuid]
 @_uuid ||= Uuid.new(read_attribute(:uuid))
 fail unless @_uuid.valid_uuid?
 @_uuid
 end

 private

 def set_uuid
 self.uuid ||= Uuid.generate.to_s
 end

end

class Record < ActiveRecord::Base
 self.abstract_class = true
 include UsesUuids
 include UsesUuids::ActiveRecord
 include UsesUuids::SetsAfterInitialize
end

class Post < Record
 has_many :comments
end

class Comment < Record
 belongs_to :post
end

post = Post.new 
# => #<Post uuid: "e2cc2bd0-6d6e-0131-2bc8-38f6b1147145", title: nil, content: nil, created_at: nil, updated_at: nil>

Post.joins(:comments).to_sql
# => "SELECT \"posts\".* FROM \"posts\" INNER JOIN \"comments\" ON \"comments\".\"post_uuid\" = \"posts\".\"uuid\""

Another noteworthy implementation: https://github.com/jashmenn/activeuuid

#rails

#active-record

#persistence