ActiveRecord extension for easy STI Delegation

gem install acts_as -v 0.6.5



Essentially, this is just a wrapper around the usual ActiveRecord::Assocations::Classmethods#belongs_to that inlines delegation of all active_record attribute setters/getters/helpers (with prefix support) and any additional methods, thus serving as a proxy for another table and model.

  • Transparently write to multiple tables from one active record model by proxying attributes and their methods through a second model.
  • Easily extract a new table from an existing table, but keep the existing API intact without breaking any consumers.
  • When using STI to maintain easy joins, this is an easy way to proxy unique child attributes through to another table for that child
  • Can help you enforce the Law of Demeter

This is designed for any belongs_to relationship where lifecycles are tightly coupled and proxying of attribute helpers from belongs_to -> has_one is desired.

(see example below and /spec for more detail)


Add this line to your application's Gemfile:

gem 'acts_as'

And then:

$ bundle


# This pattern encourages foreign keys to be stored on the STI's root table for easy reads.
# table :users
#   name :string
#   clan_id :integer
#   profile_id :integer
class User
  include ActsAs

class Rebel < User
  acts_as :profile, class_name: 'RebelProfile'
  acts_as :clan, prefix: %w( name ), with: %w( delegate_at_will )

# table :clans
#   name :string
#   strength :integer
#   cool :boolean
class Clan < ActiveRecord::Base
  has_many :rebels

  def delegate_at_will

# table :rebel_profiles
#   serial_data :string
class RebelProfile < ActiveRecord::Base
  has_one :rebel

Now a whole slew of methods related to ActiveRecord attributes are available for the fields being delegated to another table

# Fully Proxied Setters/Getters
rebel.strength = 10
rebel.clan.strength = 20
rebel.strength #=> 20

# ActiveModel::Dirty helpers
rebel.strength_was #=> 10

# Shorthand for prefix-delegating specific fields
rebel.clan_name #=>

# Automagic boolean helpers #=>

# Any method you want
rebel.delegate_at_will #=> '10'

Automagical joins through .where Hash syntax

Just get to what you want
    Rebel.where(strength: 10) #=> the same as Rebel.joins(:clan).where(clan: {strength: 10)
One major caveat, it only works for first-level attributes at the moment. (see pending spec)


  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request