mailbox model

Hi everyone,

I ran into some problems when modeling mailbox and mails. My code was like:

create_table :mailbox do |t|   t.integer :user_id # the owner of this mailbox end

create_table :mails do |t|   t.integer :sender_id   t.integer :receiver_id   t.string :title   t.text :content end

class Mailbox < ActiveRecord::Base   belongs_to :user

  has_many :sent_mails,            :class_name => 'mail',            :conditions => { :sender_id => self.user_id } # I know this is wrong

  has_many :recv_mails,            :class_name => 'mail',            :conditions => { :receiver_id => self.user_id } end

I know this is wrong. because user_id is an instance method and self refers to the class object. My question is how to fix this problem?

Thanks in advance Xiahong