Neat little STI association trick, works with to_json but finder include needs some love

sti_associations_demo.rb

# Objective: An association using STI should only query the db once for the base class

class Contact < ActiveRecord::Base
  has_many :info, :class_name=>'::Contact::ContactInfo'
  has_many :phones, :class_name=>'::Contact::Phone'
  has_many :emails, :class_name=>'::Contact::Email'
  has_many :addresses, :class_name=>'::Contact::Address'
  
  # load all info's thorugh info
  # this is possible due to how associations are mixed into the class via a module
  def info
    unless info_assoc = @association_cache[:info]
      info_assoc = self.association(:info)
      a = {:phones => [], :emails => [], :addresses => []}
      info_assoc.load_target.each do |info|
        a[:phones].push(info) and next if info.is_a?(::Contact::Phone)
        a[:emails].push(info) and next if info.is_a?(::Contact::Email)
        a[:addresses].push(info) and next if info.is_a?(::Contact::Address)
      end
      a.each { |assoc_name, records| self.association(assoc_name).target = records }
    end
    info_assoc
  end
  
  def phones; self.info; super; end
  def emails; self.info; super; end
  def addresses; self.info; super; end
  
  class ContactInfo < ActiveRecord::Base
    set_table_name "contacts_info"
  end
  
  class Email < ContactInfo
  end
  class Phone < ContactInfo
  end
  class Address < ContactInfo
  end
end

# to_json works like a charm
>> Contact.first.to_json(:include=>[:phones,:emails,:addresses])
D, [2012-03-09T02:50:21.378127 #47368] DEBUG -- :   Contact Load (0.6ms)  SELECT "contacts".* FROM "contacts" LIMIT 1
D, [2012-03-09T02:50:21.380086 #47368] DEBUG -- :   Contact::ContactInfo Load (0.5ms)  SELECT "contacts_info".* FROM "contacts_info" WHERE "contacts_info"."contact_id" = 1


# finder includes, meh...
>> Contact.first(:include=>[:phones,:emails,:addresses]).to_json(:include=>[:phones,:emails,:addresses])
D, [2012-03-09T02:46:09.721232 #47368] DEBUG -- :   Contact Load (0.7ms)  SELECT "contacts".* FROM "contacts" LIMIT 1
D, [2012-03-09T02:46:09.722783 #47368] DEBUG -- :   Contact::Phone Load (0.6ms)  SELECT "contacts_info".* FROM "contacts_info" WHERE "contacts_info"."type" IN ('Contact::Phone') AND "contacts_info"."contact_id" IN (1)
D, [2012-03-09T02:46:09.730487 #47368] DEBUG -- :   Contact::Email Load (0.4ms)  SELECT "contacts_info".* FROM "contacts_info" WHERE "contacts_info"."type" IN ('Contact::Email') AND "contacts_info"."contact_id" IN (1)
D, [2012-03-09T02:46:09.731696 #47368] DEBUG -- :   Contact::Address Load (0.4ms)  SELECT "contacts_info".* FROM "contacts_info" WHERE "contacts_info"."type" IN ('Contact::Address') AND "contacts_info"."contact_id" IN (1)
D, [2012-03-09T02:46:09.732826 #47368] DEBUG -- :   Contact::ContactInfo Load (0.3ms)  SELECT "contacts_info".* FROM "contacts_info" WHERE "contacts_info"."contact_id" = 1