Single Table Inheritance with Rails

sti-rails.rb

class User < ActiveRecord::Base
	has_many :follows
	delegate :following, :follower, to: :follows
end

class Follow < ActiveRecord::Base
	scope :following, -> { where(type: 'following') }
	scope :follower, -> { where(type: 'follower') }
end

class Following < Follow
#   write something which belongs to Following only
end

class Follower < Follow
  #   write something which belongs to Follower only
end



STI PROS:

Simple to implement
DRY — saves replicated code using inheritance and shared attributes
Allows subclasses to have own behavior as necessary

STI CONS:

Doesn’t scale well: as data grows, table can become large and possibly difficult to maintain/query
Requires care when adding new models or model fields that deviate from the shared fields
(conditional) Allows creation of invalid objects if validations are not in place
(conditional) Can be difficult to validate or query if many null values exist in table