Rails has_many :through Find by Extra Attributes in Join Model

Question

New to both Ruby and Rails but I'm book educated by now (which apparently means nothing, haha).

I've got two models, Event and User joined through a table EventUser

class User < ActiveRecord::Base
  has_many :event_users
  has_many :events, :through => :event_users
end

class EventUser < ActiveRecord::Base
  belongs_to :event
  belongs_to :user

  #For clarity's sake, EventUser also has a boolean column "active", among others
end

class Event < ActiveRecord::Base
  has_many :event_users
  has_many :users, :through => :event_users
end

This project is a calendar, in which I have to keep track of people signing up and scratching their name out for a given event. I figure the many to many is a good approach, but I can't do something like this:

u = User.find :first
active_events = u.events.find_by_active(true)

Because events don't actually HAVE that extra data, the EventUser model does. And while I could do:

u = User.find :first
active_events = []
u.event_users.find_by_active(true).do |eu|
  active_events << eu.event
end

This seems to be contrary to "the rails way". Can anyone enlighten me, this has been bugging me for a long time tonight (this morning)?

Answer 1

How about adding something like this into your User model?

has_many  :active_events, :through => :event_users, 
          :class_name => "Event", 
          :source => :event, 
          :conditions => ['event_users.active = ?',true]

After that you should be able to get active events for a user just by calling:

User.first.active_events