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from django.db import models | |
# http://www.djangosnippets.org/snippets/562/#c673 | |
# https://gist.github.com/fission6/2587518 | |
class QuerySetManager(models.Manager): | |
# http://docs.djangoproject.com/en/dev/topics/db/managers/#using-managers-for-related-object-access | |
# Only works for OneToOne relations...: | |
# https://code.djangoproject.com/ticket/14891 | |
use_for_related_fields = True | |
def __init__(self, qs_class=models.query.QuerySet): | |
super(QuerySetManager, self).__init__() | |
self.queryset_class = qs_class | |
self.custom_methods = [a for a in qs_class.__dict__ if not a.startswith('_')] | |
def get_queryset(self): | |
return self.queryset_class(self.model) | |
def __getattr__(self, attr, *args): | |
# Allow shallow copy: https://code.djangoproject.com/ticket/15062 | |
if attr in self.custom_methods: | |
return getattr(self.get_queryset(), attr, *args) | |
else: | |
return getattr(self.__class__, attr, *args) | |
class QuerySet(models.query.QuerySet): | |
"""Base QuerySet class for adding custom methods that are made | |
available on both the manager and subsequent cloned QuerySets""" | |
@classmethod | |
def as_manager(cls, ManagerClass=QuerySetManager): | |
return ManagerClass(cls) | |
""" | |
Example | |
class MerchantQuerySet(QuerySet): | |
def live(self): | |
return self.filter(live=True) | |
def locked(self): | |
return self.filter(locked=True) | |
def unlocked(self): | |
return self.filter(locked=False) | |
class Merchant(models.Model): | |
created_on = models.DateTimeField(auto_now_add=True) | |
modified = models.DateTimeField(auto_now=True) | |
name = models.CharField(max_length=200) | |
live = models.BooleanField(default=False) | |
locked = models.BooleanField(default=True) | |
objects = MerchantQuerySet.as_manager() | |
We can now do | |
Merchant.objects.live().locked() | |
or | |
Merchant.objects.live() | |
or | |
Merchant.objects.live().unlocked() | |
etc ... | |
""" |
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