Question

This is a little bit tricky, so if you need more information, don’t hesitate!

I have two models, Store and Consumer that are linked by two ways:

1/ Store and Consumer inherite from the same model Profile, because they share many attributes (name, location, email, web page,…). Here is the Rails AR code:

class Profile << ActiveRecord::Base
    # Attributes and validation rules go here.
end

class Store << Profile
end

class Consumer << Profile
end

This is the well known Single Table Inheritance (STI).

2/ In addition to STI, Store and Consumer are linked by a many to many relation:

• Store has many Clients (many consumers)

• A consumer is client to many stores

Because I need more attributes for this link (Store – Consumer), I have to create an extra model that will link them: Client.

Here are my final AR models:

class Profile << ActiveRecord::Base
    # Attributes and validation rules go here.
end

class Store << Profile
    has_many :clients
end

class Consumer << Profile
    has_many :clients
end

class Client << ActiveRecord::Base
    belongs_to :store
    belongs_to :consumer
end

Problem

Using STI doesn’t create store_id and consumer_id… we have only profile_id (because one real table Profile). So, how can I target the correct Client row having both store_id and client_id ?

Any idea how to do that? Thanks in advance.

Answer 1

I think you want to do is something like this. Also, I agree with Daniel Wright’s comment.

class Profile << ActiveRecord::Base
    belongs_to :store
    belongs_to :consumer
end

class Store << ActiveRecord::Base
    has_one :profile
    has_many :clients
    has_many :consumers, :through => :clients
end

class Consumer << ActiveRecord::Base
    has_one :profile
    has_many :clients
    has_many :stores, :through => :clients
end

class Client << ActiveRecord::Base
    belongs_to :store
    belongs_to :consumer
end

But if you’d like to make it work with what you have you could do something like:

class Profile << ActiveRecord::Base

end

class Store << Profile
    has_many :clients, :foreign_key => 'store_id'
    has_many :consumers, :through => :clients
end

class Consumer << Profile
    has_many :clients, :foreign_key => 'consumer_id'
    has_many :stores, :through => :clients
end

class Client << ActiveRecord::Base
    belongs_to :store
    belongs_to :consumer
end