HABTM Polymorphic Relationship

I'm pretty new to Rails, and i'm trying to do a polymorphic HABTM relationship. The problem is that I have three models that I want to relate.

The first one is the Event model and then are two kind of attendees: Users and Contacts.

What I want to do is to be able to relate as an attendee both users and contacts. So, what i have right now in my code is:

Event Model

has_and_belongs_to_many :attendees, :polymorphic => true

User Model

has_and_belongs_to_many :events, :as => :attendees

Contact Model

has_and_belongs_to_may :events, :as => :attendees

1. How the HABTM table migration needs to be? I'm a little confused and i have found no help on th开发者_JAVA技巧at.
2. Is it going to work?

No, you can't do that, there's no such thing as a polymorphic has_and_belongs_to_many association.

What you can do is create a middle model. It would probably be something like this:

class Subscription < ActiveRecord::Base
  belongs_to :attendee, :polymorphic => true
  belongs_to :event
end

class Event < ActiveRecord::Base
  has_many :subscriptions
end

class User < ActiveRecord::Base
  has_many :subscriptions, :as => :attendee
  has_many :events, :through => :subscriptions
end

class Contact < ActiveRecord::Base
  has_many :subscriptions, :as => :attendee
  has_many :events, :through => :subscriptions
end

This way the Subscription model behaves like the link table in a N:N relationship but allows you to have the polymorphic behavior to the Event.

Resolveu parcialmente.

It does solve the problem given the framework that we have at our disposal, but it adds "unnecessary" complexity and code. By creating an intermediary model (which I will call B), and given A -> B -> C being "A has_many B's which has_many C's", we have another AR Model which will load one more AR class implementation into memory once it is loaded, and will instantiate for the sole purpose of reaching C instances. You can always say, if you use the :through association, you don't load the B association, but then you'll be left with an even more obsolete model, which will only be there to see the caravan pass by.

In fact, this might be a feature that is missing from Active Record. I would propose it as a feature to add, since it has been cause of concern for myself (that's how I landed in this post hoping to find a solution :) ).

Cumprimentos