gistfile1.txt

require 'rubygems'
require 'dm-core'
require 'dm-more'
require 'dm-timestamps'
require 'dm-is-versioned'

DataMapper.setup(:sqlite3, 'sqlite3::memory:')
DataMapper::Repository.adapters[:default] =  DataMapper::Repository.adapters[:sqlite3]
DataMapper::Logger.new(STDOUT, :debug)
DataObjects::Sqlite3.logger = DataObjects::Logger.new(STDOUT, :debug)
 
class Story
  include DataMapper::Resource
 
  property :id, Integer, :serial => true
  property :title, String
  property :updated_at, DateTime
 
  before :save do
    # For the sake of testing, make sure the updated_at is always unique
    time = self.updated_at ? self.updated_at + 1 : Time.now
    self.updated_at = time if self.dirty?
  end
 
  is_versioned :on => :updated_at
 
end

Story.auto_migrate!

story = Story.new
story.title = "New Title"
story.save # => Saves this story and creates a new version with the
           #    original values.
story.versions.size # => 1

story.title = "A Different New Title"
story.save
story.versions.size # => 2