Datamapper's hooks won't work

Can't understand why hooks don't work. I have the following model:

class DirItem
  include DataMapper::Resource

  # property <name>, <type>
  property :id, Se开发者_如何学Crial
  property :dir_cat_id, Integer, :required => true
  property :title, String, :required => true
  property :price, Integer, :default => 0

  belongs_to :dir_cat
  has n, :dir_photos
  has n, :dir_field_values

  before :destroy do
    logger.debug "==============DESTROYING ITEM ##{id}, TITLE
#{title}"
    dir_field_values.destroy
    dir_photos.destroy
  end
end

When I call destroy method either from my app or irb, it returns false. The errors hash is empty, the log message doesn't print and the record won't delete.

This hook works for me (ruby 1.9.2 / DM 1.0.2):

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


# setup the logger
DataMapper::Logger.new($stdout, :debug)

# connect to the DB
DataMapper.setup(:default, 'sqlite3::memory:')

class DirItem
  include DataMapper::Resource

  # property <name>, <type>
  property :id, Serial
  property :dir_cat_id, Integer, :required => true
  property :title, String, :required => true
  property :price, Integer, :default => 0

  has n, :dir_photos

  before :destroy do
    dir_photos.destroy
  end
end

class DirPhoto
  include DataMapper::Resource
  property :id, Serial
  belongs_to :dir_item
end

DataMapper.finalize.auto_migrate!

@i = DirItem.create(:title => 'Title', :dir_cat_id => 1)
@i.dir_photos.create
@i.dir_photos.create
@i.dir_photos.create
@i.destroy

The DM logger reveals that each of the dir_photos are destroyed before the dir_item is. Instead of using hooks, you might want to look into using dm-constraints though. With something like:

has n, :dir_photos, :constraint => :destroy

you can be sure that all the dir_photos will be destroyed when the dir_item is destroyed, and this will also be enforced by database level foreign key constraints.