has_many

gistfile1.rb

create_table "messages", :force => true do |t|
  t.string   "subject"
  t.text     "body"
  t.datetime "created_at"
  t.datetime "updated_at"
  t.string   "message_type"
  t.integer  "user_id"
  t.boolean  "deleted", :default => false
end

class User < ActiveRecord::Base
  has_many :messages
end

class Messages < ActiveRecord::Base
  MESSAGE_TYPES = %w[Recipient Author]

  belongs_to :user

  named_scope :recipient, :conditions => {:message_type => 'Recipient'}
  named_scope :author, :conditions => {:message_type => 'Author'}
  named_scope :deleted, :conditions => {:deleted => true}
  named_scope :not_deleted, :conditions => {:deleted => false}

  # Convenience class methods
  def self.sent
    author.not_deleted
  end

  def self.received
    recipient.not_deleted
  end
end

# Example usage
user = User.first
user.messages.sent
user.messages.received
user.messages.deleted