This is probably not a bug and just a consequence of what I'm trying to do (and probably not doing it in a very good way), so this is not me saying "something needs to be fixed or changed", just observing.
I have a model class of "Document" which has a file field on it and is set up to have a GenericForeignKey field which can be blank. I have a variety of other classes which have GenericRelation fields to point back to it. What I want to do is treat them a bit like a ManyToMany field on a form. The UI for the GenericRelation fields that point to documents consists of listing any existing documents set in the field, allowing documents to be removed from the field and also providing a popup dialogue which allows new documents to be created (they get saved through the popup dialogue but with the GenericForeignKey field set to blank). The first thing I hit was that "GenericRelation" fields are forced to to have "editable" set to False, so the model form creation skips 'em. So I declared them on the form as ModelMultipleChoiceField (for the purposes of having something vaguely sensible there) but using my own custom code to render the widget. When the form is submitted the value for the widget consists of id values for the Document objects selected and ModelMultipleChoiceField's clean method turns it into a list of Document objects. So far so good. save_m2m fires and so __set__ gets called for the GenericRelation field and that's where I hit a problem because __set__ assumes that the value being assigned to it contains none of the prior values so calls .clear() before then doing .add() for each item. So if you had a field called "somegenericrelation" on an instance which had some values (i.e. objects related via the relation) then doing "instance.somegenericrelation=instance.somegenericrelation" will delete all the items and then add them ... Now as ..save() on a model instance will do an "INSERT" if the record doesn't exist when what would happen usually is that the table entries (in my case for Document) would be deleted and reinserted. As "Document" has a file field what happens is the file gets deleted on disk by the file manager during the deletion and then of course although the record for the Document gets recreated the file is now gone. So from this I suspect having a GenericRelation field appear on a form is bad and I'm probably doing something I shouldn't - alternatively maybe it's an area/use of contenttypes that's been overlooked? I also suspect that assigning to a GenericRelation field a list of values that includes items already assigned to it is bad and shouldn't be done (and because I'm doing a bad thing in using it on a form I'm making the django form stuff do this bad thing itself) - alternatively maybe __set__ on ReverseGenericRelatedObjectsDescriptor could be a bit more clever and not delete any objects its going to add back again with .add. Matt --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-users@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/django-users?hl=en -~----------~----~----~----~------~----~------~--~---
