Demonstrates a problem I am having with associations in datamapper

test_association.rb

#! /usr/bin/env ruby

require 'dm-core'

class Foo
  include DataMapper::Resource

  property :id, Serial

  has n, :foo_bars
  has n, :bars, through: :foo_bars
end

class Bar
  include DataMapper::Resource

  property :id, Serial

  has n, :foo_bars
  has n, :foos, through: :foo_bars
end

class FooBar
  include DataMapper::Resource

  property :foo_id, Integer, key: true, min: 1
  property :bar_id, Integer, key: true, min: 1

  belongs_to :foo, key: true
  belongs_to :bar, key: true
end

DataMapper.finalize

# works...