class Person < ActiveRecord::Base has_many :readers has_many :posts, :through => :readers has_many :posts_with_no_comments, :through => :readers, :source => :post, :include => :comments, :conditions => 'comments.id is null' has_many :references has_many :jobs, :through => :references has_one :favourite_reference, :class_name => 'Reference', :conditions => ['favourite=?', true] end