Single Table Inheritance example¶ ↑

This is a sample sti application to demonstrate Single Table Inheritance(STI) in Rails. There are two main models User and Address, Address model has a type for HomeAddres, PreferredAddress and WorkAddress via STI

User model:

# == Schema Information
#
# Table name: users
#
#  id         :integer         not null, primary key
#  first_name :string(255)
#  last_name  :string(255)
#  email      :string(255)
#  created_at :datetime
#  updated_at :datetime
#
class User < ActiveRecord::Base
  has_many :addresses, :dependent => :delete_all
  has_one  :home_address
  has_one  :preferred_address
  has_one  :work_address

  accepts_nested_attributes_for :home_address, :preferred_address, :work_address
end

Address model:

# == Schema Information
#
# Table name: addresses
#
#  id         :integer         not null, primary key
#  street     :string(255)
#  city       :string(255)
#  state      :string(255)
#  postal     :string(255)
#  country    :string(255)
#  type       :string(255)
#  user_id    :integer
#  created_at :datetime
#  updated_at :datetime
#
class Address < ActiveRecord::Base
  belongs_to :user
end

And here is STI for HomeAddress, PreferredAddress and WorkAddress from the Address Model:

class HomeAddress < Address
end

class PreferredAddress < Address
end

class WorkAddress < Address
end

Installing¶ ↑

run rake db:migrate

Web Server¶ ↑

Example of usage:

run script/server

go to: localhost:3000/users/new

Console¶ ↑

Example of usage in console:

run script/console

# creata a user

>> viola = User.create(:first_name => "Viola", :last_name => "Holownia", :email => "[email protected]")
  User Create (0.5ms)   INSERT INTO "users" ("updated_at", "first_name", "last_name", "email", "created_at") VALUES('2010-02-26 06:39:22', 'Viola', 'Holownia', '[email protected]', '2010-02-26 06:39:22')
=> #<User id: 16, first_name: "Viola", last_name: "Holownia", email: "[email protected]", created_at: "2010-02-26 06:39:22", updated_at: "2010-02-26 06:39:22">

# create a home address for user viola

>> viola.create_home_address(:city => "Home City", :postal => "73-100", :country => "Home Country")
  HomeAddress Create (9.7ms)   INSERT INTO "addresses" ("city", "postal", "updated_at", "country", "type", "street", "user_id", "state", "created_at") VALUES('Stargard', '73-100', '2010-02-26 06:40:51', 'Poland', 'HomeAddress', NULL, 16, NULL, '2010-02-26 06:40:51')
=> #<HomeAddress id: 48, street: nil, city: "Stargard", state: nil, postal: "73-100", country: "Poland", type: "HomeAddress", user_id: 16, created_at: "2010-02-26 06:40:51", updated_at: "2010-02-26 06:40:51">

# create a prefrerred address for user viola

>> viola.create_preferred_address(:city => "Ithaca", :state => "NY", :postal => "14850", :country => "USA")
=> #<PreferredAddress id: 49, street: nil, city: "Ithaca", state: "NY", postal: "14850", country: "USA", type: "PreferredAddress", user_id: 16, created_at: "2010-02-26 06:41:54", updated_at: "2010-02-26 06:41:54">

# get all addresses for user viola

>> viola.addresses
  Address Load (0.6ms)   SELECT * FROM "addresses" WHERE ("addresses".user_id = 16) 
=> [#<HomeAddress id: 48, street: nil, city: "Stargard", state: nil, postal: "73-100", country: "Poland", type: "HomeAddress", user_id: 16, created_at: "2010-02-26 06:40:51", updated_at: "2010-02-26 06:40:51">, #<PreferredAddress id: 49, street: nil, city: "Ithaca", state: "NY", postal: "14850", country: "USA", type: "PreferredAddress", user_id: 16, created_at: "2010-02-26 06:41:54", updated_at: "2010-02-26 06:41:54">]

# get a count of addresses for user viola

>> viola.addresses.count
  SQL (0.3ms)   SELECT count(*) AS count_all FROM "addresses" WHERE ("addresses".user_id = 16) 
=> 2

# get a home address for user viola

>> viola.home_address
=> #<HomeAddress id: 48, street: nil, city: "Stargard", state: nil, postal: "73-100", country: "Poland", type: "HomeAddress", user_id: 16, created_at: "2010-02-26 06:40:51", updated_at: "2010-02-26 06:40:51">

# is work address blank for user object viola?

>> viola.work_address.blank?
  WorkAddress Load (0.4ms)   SELECT * FROM "addresses" WHERE ("addresses".user_id = 16) AND ( ("addresses"."type" = 'WorkAddress' ) ) LIMIT 1
=> true

# find all users with home address

>> User.find(:all, :joins => :home_address)
  User Load (0.6ms)   SELECT "users".* FROM "users" INNER JOIN "addresses" ON addresses.user_id = users.id AND ("addresses"."type" = 'HomeAddress' ) 
=> [#<User id: 16, first_name: "Viola", last_name: "Holownia", email: "[email protected]", created_at: "2010-02-26 06:39:22", updated_at: "2010-02-26 06:39:22">, #<User id: 17, first_name: "Bob", last_name: "Awesome", email: "[email protected]", created_at: "2010-02-26 06:45:02", updated_at: "2010-02-26 06:45:02">]

# find all users with work address

>> User.find(:all, :joins => :work_address)
  User Load (0.3ms)   SELECT "users".* FROM "users" INNER JOIN "addresses" ON addresses.user_id = users.id AND ("addresses"."type" = 'WorkAddress' ) 
=> []

# destroy user viola, note: b/c we put has_many :addresses, :dependent => :delete_all in user model it will also destroy all addresses associated with user object viola

>> viola.destroy
  Address Delete all (0.6ms)   DELETE FROM "addresses" WHERE ((user_id = 16)) 
  User Destroy (0.1ms)   DELETE FROM "users" WHERE "id" = 16
=> #<User id: 16, first_name: "Viola", last_name: "Holownia", email: "[email protected]", created_at: "2010-02-26 06:39:22", updated_at: "2010-02-26 06:39:22">