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
run rake db:migrate
Example of usage:
run script/server
go to: localhost:3000/users/new
Example of usage in console:
run script/console
# creata a user
>> viola = User.create(:first_name => "Viola", :last_name => "Holownia", :email => "viola.holownia@example.com")
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', 'viola.holownia@example.com', '2010-02-26 06:39:22')
=> #<User id: 16, first_name: "Viola", last_name: "Holownia", email: "viola.holownia@example.com", 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: "viola.holownia@example.com", 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: "bob@awesome.com", 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: "viola.holownia@example.com", created_at: "2010-02-26 06:39:22", updated_at: "2010-02-26 06:39:22">