I tried a different and actually a lot more sensible approach as follows:
my_hash.each do |id, some_string_that_is_irrelevant|
album_photo = album.album_photos.first(:photo_id=>id) #Didn't want
to reach to the database for an actual Photo instance
album_photo.position = position
position += 1
end
However, I still get DataMapper::UpdateConflictError: Book#update cannot be
called on a dirty resource
This really boggles my mind because all I am doing is updating a single
non-PK attribute through the API.
If anyone sees something I am missing, I would appreciate the help.
Thanks.
On Saturday, April 21, 2012 1:30:57 AM UTC-4, Neil Chaudhuri wrote:
>
> I need to store people, albums, photos, and the order that photos
> appear in an album, so I decided to try adding a "position" attribute
> to the association between Photo and Album. Consider the following
> models:
>
> class Person
> include DataMapper::Resource
> ...
> end
>
> class Album
> include DataMapper::Resource
> ...
> has n, :photos, "Photo", :through => :album_photos, :via => :photo
> end
>
> class Photo
> include DataMapper::Resource
> ...
>
> belongs_to :person, :required => true
> has n, :albums, "Album", :through => :album_photos, :via => :album
> end
>
> class AlbumPhoto
> include DataMapper::Resource
>
> property :position, Integer, :default => 1
>
> belongs_to :album, :key => true
> belongs_to :photo, :key => true
>
> end
>
> First, is such the right way to achieve this sort of thing? I didn't
> see anything like this in the documentation.
>
> To add a wrinkle, I have a model called Book which has a 1:M
> relationship with Album. When I execute the following code
>
> album.album_photos.destroy
> album.album_photos << AlbumPhoto.new({:position =>3})
> book.update
>
> I get "DataMapper::UpdateConflictError: Book#update cannot be called
> on a dirty resource"
>
> I am curious if my models are defined correctly. If so, how can I
> delete all prior associations and update their positions "cleanly"?
>
> Thanks.
>
>
>
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