gistfile1.rb

class Product
  include DataMapper::Resource

  property :id,          Serial
  property :title,       String, :required => true
  property :description, Text,   :required => true

  has n, :variants

  after :create, :make_master_variant

  def make_master_variant
    self.variants.create(:sku => "cf-19")
  end

  def html_description
    Redcarpet.new(description).to_html
  end
end