This question on SO appears to be related to my question, but I\'m not sure my question is answered by that.
An address can belong to more than one model (UserProfile an
You missed one option: have a class that contains the common behavior and add the fields to all tables. Use a composed_of aggregate to manage the data.
class Address
attr_accessor :line1, :line2, :city, :state, :zip
def initialize(line1, line2, city, state, zip)
@line1 = line1
end
end
class UserProfile < ActiveRecord::Base
composed_of :address, :mapping => %w(line1 line2 city state zip)
end
class Event < ActiveRecord::Base
composed_of :address, :mapping => %w(line1 line2 city state zip)
end
See #composed_of in the Ruby on Rails API docs.
One way would be standard Rails polymorphism:
class Address
belongs_to :addressable, :polymorphic => true
end
class UserProfile
has_one address, :as => :addressable
end
class Event
has_one address, :as => :addressable
end
It could be the nagging feeling you have about this is that you can't create a db-level constraint with Rails-style polymorphic relationships. The alternative (suggested by Dan Chak in Enterprise Rails) is like your #1 option, where you do indeed create a separate id field for each type of relationship. This does leave unused fields, but it also allows for constraints. I can see the argument for both, but the Rails community has been using AR polymorphism for some time with apparently good success. I use it without hesitation. But if that bugs you, you can use Chak's approach. It's a lot more work. : )
EDIT: @Slick86, migration would look something like:
class CreateAddresses < ActiveRecord::Migration
def change
create_table :addresses do |t|
t.integer :addressable_id
t.string :addressable_type
end
end
end