I'm referring to the code snippet in the first answer taken from this post: Custom QuerySet and Manager without breaking DRY?
from django.db import models
from django.db.models.query import QuerySet
class CustomQuerySetManager(models.Manager):
"""A re-usable Manager to access a custom QuerySet"""
def __getattr__(self, attr, *args):
try:
return getattr(self.__class__, attr, *args)
except AttributeError:
return getattr(self.get_query_set(), attr, *args)
def get_query_set(self):
return self.model.QuerySet(self.model)
Here is the model:
from custom_queryset.models import CustomQuerySetManager
from django.db.models.query import QuerySet
class Inquiry(models.Model):
objects = CustomQuerySetManager()
class QuerySet(QuerySet):
def active_for_account(self, account):
se开发者_运维百科lf.filter(account = account, deleted=False, *args, **kwargs)
self.model.QuerySet(self.model)
always receives a same model, but the result QuerySet depends on the input QuerySet. For example:
Inquiry.objects.all()[:5].active_for_account(xyz)
, then active_for_account
will receive a query set of 5 items, while in Inquiry.objects.all()[:7].active_for_account(xyz)
, active_for_account
will receive a query set of 7 items. Here are stack traces:
Inquiry.objects.all()[:5].active_for_account(xyz)
return getattr(self.get_query_set(), attr, *args),
return self.model.QuerySet(self.model) (1)
Inquiry.objects.all()[:7].active_for_account(xyz)
return getattr(self.get_query_set(), attr, *args),
return self.model.QuerySet(self.model) (2)
Why are results at (1) and (2) different?
I'm not entirely sure what you're asking here.
Inquiry.objects.all()[:5]
doesn't give you give objects, it gives you a single QuerySet object which contains five elements.
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