Datamapper的钩子不起作用

Question

无法理解为什么钩子不起作用.我有以下型号:

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

  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

当我destroy从我的应用程序或irb 调用方法时,它返回false.该errors哈希为空,则日志消息不打印和记录将不会删除.

Answer 1

这个钩子适合我(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

DM记录器显示每个dir_photos在dir_item之前被销毁.您可能希望查看使用钩子而不是使用钩子dm-constraints.有类似的东西:

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

您可以确保在销毁dir_item时将销毁所有dir_photos,并且这也将由数据库级外键约束强制执行.