gistfile1.rb

DataMapper::Logger.new(STDOUT, :debug)
DataMapper.setup(:default, 'sqlite3:///tmp/bug.db')

class Sheep
  include DataMapper::Resource
  
  property :id, Serial
  property :name, String, :unique_index => true

  has n, :fleas

  before :save do
    puts "sheep before save..."
  end
end

class Flea
  include DataMapper::Resource

  property :id, Serial
  property :position, String

  belongs_to :sheep, :required => false

  before :save do
    puts "flea before save..."
  end
end

DataMapper.auto_migrate!
@sheep = Sheep.new(:name => 'Shaun')
50.times { |i| @sheep.fleas.build(:position => i.to_s) }