Django: How do you access a model's instance from inside a manager?
class SupercalifragilisticexpialidociousManager(models.Manager):
# Sorry, I'm sick of Foo and Spam for now.
def get_query_set(self, account=None):
return super(SupercalifragilisticexpialidociousManager,
self).get_query_set().filter(uncle开发者_StackOverflow=model_thats_using_this_manager_instance.uncle)
The magic I'm looking for is the "uncle=model_thats_using_this_manager_instance.uncle". It seems like I should be able to do this somehow. I know I could say self.model
to get the model, but how to get the instance?
It doesn't make sense to ask for an instance when you're using a manager. Managers are class-level attributes - if you try and do foo.objects.all()
where foo
is an instance of Supercalifragilisticexpialidocious, you will explicitly get an error:
AttributeError: Manager isn't accessible via Supercalifragilisticexpialidocious instances
As far as I know, you cannot access the model from inside a manager. It doesn't make sense as managers operate on the whole table.
You should do something like this in the model:
class Model(models.Model):
# some attributes here
def getAllRelativesWithSameUncle(self):
return Model.objects.filter(uncle = self.uncle)
or in the manager:
class SupercalifragilisticexpialidociousManager(models.Manager):
def getSelfRelativesFor(self, model):
return self.get_queryset().filter(uncle=model)
In methods like object.related_name.create()
under the hood the Djangos sends a hint
argument:
class UserQuerySet(QuerySet):
def create(self, *args, **kwargs):
print(self._hints)
# >>> {'instance': <User: random-user>}
print(self._hints.get('instance'))
# >>> <User: random-user>
I'm using Django 1.11 nowadays.
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