Question

Using Datamapper, I have a model Album that has n, :photos which has a Paperclip::Resource

With ActiveRecord I would just have had:

has_many :photos, dependent: :destroy

in my Album model, in order to delete the photos at the same time as the Album, but with Datamapper it seems you have to roll your own. In Sinatra, to delete the album I have:

delete '/albums/:id' do
  a = Album.get params[:id] 
  a.destroy
  redirect '/'
end

and a before filter in the Album model:

before :destroy do
  photos.destroy
end

but the before filter is never called.

If I put use the bang method, a.destroy!, the album is destroyed but not the Photos.

No errors are produced and no Exceptions raised.

UPDATE

There are errors, but with an empty errors hash:

INFO -- : #<DataMapper::Validations::ValidationErrors:0x13740dc @resource=#<Album @id=2 @name="Quaver" @created_at=#<DateTime: 2013-02-07T10:30:36+00:00 (5895194251/2400,0/1,2299161)> @updated_at=#<DateTime: 2013-02-07T10:30:36+00:00 (5895194251/2400,0/1,2299161)>>, @errors={}>

So clearly I have validation issues. However I have not set any validations in my Models:

class Photo  
  include DataMapper::Resource
  include Paperclip::Resource  

  property :id, Serial
  property :title, String
  property :created_at, DateTime  
  property :updated_at, DateTime

  has_attached_file :data, url: "/:attachment/:id/:style/:basename.:extension",
                       path: "#    {APP_ROOT}/public/:attachment/:id/:style/:basename.:extension"
  belongs_to :album
end

class Album  
  include DataMapper::Resource  
  property :id, Serial
  property :name, String
  property :created_at, DateTime  
  property :updated_at, DateTime
  has n, :photos

  before :destroy do
    photos.destroy
  end
end

So the before filter is not being called because of the ValidationErrors, but where do they come from when they are not explicitly set?

Any help, gratefully received. Thanks.

Answer 1

Apparently when you use:

require 'data_mapper'

you are implicitly using dm-constraints, which protects dependent models by default. Simply giving permission to destroy (much like ActiveRecord) does the trick:

has n, :photos, constraint: :destroy

Damn that hurt!