gistfile1.rb

require 'rubygems'

gem 'dm-core'
gem 'dm-types'
require 'dm-core'
require 'dm-types'

class User
  include DataMapper::Resource

  property :id, DM::UUID, :key => true, :unique_index => true, :default => lambda { ::UUID.random_create }
  property :name, String
  has n, :accounts
end


class Account
  include DataMapper::Resource
  property :id, DM::UUID, :key => true, :unique_index => true, :default => lambda { ::UUID.random_create }
  property :code, String
  belongs_to :user
end

DataMapper.setup(:default, 'sqlite3::memory:')
DataMapper.auto_migrate!

u = User.create(:name => 'test')

# this works
p Account.create(:user => u, :code => '123')

# this doesn't
p u.accounts.create(:code => '123')