gistfile1.rb

#!/usr/bin/env ruby -Ku

# encoding: utf-8

require 'rubygems'
require 'dm-core'
require 'dm-migrations'

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

class Customer
  include DataMapper::Resource

  property :id,   Serial
  property :name, String, :required => true, :length => 1..100

  has n, :orders
  has n, :items, :through => :orders
end

class Order
  include DataMapper::Resource

  property :id,        Serial
  property :reference, String, :required => true, :length => 1..20

  belongs_to :customer

  has n, :order_lines
  has n, :items, :through => :order_lines
end

class OrderLine
  include DataMapper::Resource

  property :id,         Serial
  property :quantity,   Integer, :required => true, :default => 1, :min => 1
  property :unit_price, Decimal, :required => true, :default => lambda { |r,p| r.item.unit_price }

  belongs_to :order
  belongs_to :item
end

class Item
  include DataMapper::Resource

  property :id,         Serial
  property :sku,        String,  :required => true, :length => 1..20
  property :unit_price, Decimal, :required => true, :min => 0

  has n, :order_lines
end

DataMapper.auto_migrate!

puts '-' * 80

customer = {
  :name   => 'Dan Kubb',
  :orders => [
    {
      :reference   => 'TEST1234',
      :order_lines => [
        {
          :item => {
            :sku        => 'BLUEWIDGET1',
            :unit_price => 1.00,
          },
        },
      ],
    },
  ]
}

# create the Customer with a nested options
Customer.create(customer)

puts '-' * 80

# the options to create can be used to retrieve the same object
p Customer.all(customer)