Django GenericRelation doesn't save related object's id - is this a bug or am I doing it wrong?
- by pinkeen
I have a model with a generic relation (call it A), when creating an instance of this object I pass an instance of another model (call it B) as the initializer of the content_object field (via kwargs of the constructor).
If I don't save B before creating A then when saving A the content_object_id is saved to the db as NULL. If I save B before passing it to the constructor of A then everything's allright.
It's not logical. I assumed that the ID of the related object (B) is fetched when doing A.save() and it should throw some kind of an exception if B isn't saved yet but it just fails silently. I don't like the current solution (saving B beforhand) because we don't know yet if I will be always willing to keep the object, not just scrap it, and there are performance considerations - what if I will add some another data and save it once more shortly after.
class BaseNodeData(models.Model):
...
extnodedata_content_type = models.ForeignKey(ContentType, null=True)
extnodedata_object_id = models.PositiveIntegerField(null=True)
extnodedata = generic.GenericForeignKey(ct_field='extnodedata_content_type', fk_field='extnodedata_object_id')
class MarkupNodeData(models.Model):
raw_content = models.TextField()
Suppose we do:
markup = MarkupNodeData(raw_content='...')
base = BaseNodeData(..., extnodedata=markup)
markup.save()
base.save()
# both records are inserted to the DB but base is stored with extnodedata_object_id=NULL
markup = MarkupNodeData(raw_content='...')
base = BaseNodeData(..., extnodedata=markup)
base.save()
markup.save()
# no exception is thrown and everything is the same as above
markup = MarkupNodeData(raw_content='...')
markup.save()
base = BaseNodeData(..., extnodedata=markup)
base.save()
# this works as expected
Of course I can do it this way, but it doesn't change anything:
base = BaseNodeData(...)
base.extnodedata = markup
My question is - is this a bug in django which I should report or maybe I'm doing something wrong. Docs on GenericRelations aren't exactly verbose.
