gistfile1.txt

require 'rubygems'
require 'dm-core'

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

class Zoo
  include DataMapper::Resource

  property :id, Serial
  property :name, String
  
  has n, :animals
end

class Animal
  include DataMapper::Resource
  property :id, Serial
  property :species, String
  belongs_to :zoo

end

DataMapper.auto_migrate!
Zoo.create(:name => "old").animals.create(:species => "tiger")

animal = Zoo.first.animals.first
animal.zoo.name = "new!"
puts animal.zoo.save # "true"
puts animal.zoo.name # "new!"
puts animal.zoo.dirty? # "true"
puts animal.zoo.reload.name # "old"