standalone_example.rb

#!/usr/bin/env ruby -Ku

# encoding: utf-8

require 'rubygems'
require 'dm-core'

DataMapper::Logger.new($stdout, :debug)
DataMapper.setup(:default, 'sqlite3::memory:')

class Person
  include DataMapper::Resource

  property :id, Serial
  property :name, String
  
  has n, :mailers

  has n, :mailer_people
  has n, :conversations, 'Mailer', :through => :mailer_people, :via => :mailer
end

class MailerPerson
  include DataMapper::Resource

  property :person_id, Integer, :min => 1, :key => true
  property :mailer_id, Integer, :min => 1, :key => true

  belongs_to :person
  belongs_to :mailer
end

class Mailer
  include DataMapper::Resource

  property :id, Serial
  
  belongs_to :person
  
  has n, :mailer_people
  has n, :people, :through => :mailer_people
end

DataMapper.auto_migrate!
p = Person.new(:name => 'Austin')
p.save    
p = Person.new(:name => 'Jon')
p.save
p = Person.new(:name => 'Jon')
p.save

Mailer.create(:people => Person.all(:name => 'Jon'), :person => Person.first())
Mailer.create(:people => Person.all(:name => 'Jon'), :person => Person.first())
p Mailer.first().people

p Mailer.first().person # Austin
p Mailer.get(2).person # Jon, WAht!?