Django Custom Queryset Mixin and manager

README

Based of custom chainable querysets that others have posted + the usage of mixins like the ones found in Django's class based views



Example Queryset:
    from django.db import models

    class ExchangeQuerySet(models.query.QuerySet):
        def my_test(self):
            return self.filter()

        def tester(self):
            return self.filter()





Usage 1:
    from queryset import MyQuerySet
    from managers import CustomQuerysetManager

    class MyModel(models.Model):
        objects = CustomQuerysetManager(queryset_class=MyQuerySet)

Usage 2:
    from queryset import MyQuerySet

    class MyManger(CustomQuerysetMixin, models.Manager):
      queryset_class = MyQuerySet


    class MyModel(models.Model):
        objects = MyManager()


MyModel.objects.my_test()
MyModel.objects.tester()
MyModel.objects.filter(something=something).my_test().tester().tester()


Problems:
   I haven't check the cause but it doesn't work on abstract models(abstract=True).

managers.py

from django.db import models

from queryset import CustomQuerysetMixin
            
class CustomQuerysetManager(CustomQuerysetMixin, models.Manager):
    pass

queryset.py

from django.core.exceptions import ImproperlyConfigured


class CustomQuerysetMixin(object):
    queryset_class = None
    
    def __init__(self, *args, **kwargs):
        if self.queryset_class is None:
            self.queryset_class = kwargs.pop('queryset_class', None)
        super(CustomQuerysetMixin, self).__init__(*args, **kwargs)
    
    def get_queryset_class(self):
        if self.queryset_class:
            qs = self.queryset_class
        else:
            raise ImproperlyConfigured('Provide queryset_class or override get_queryset_class().')
        return qs

    def get_query_set(self):
        return self.get_queryset_class()(self.model)

    def __getattr__(self, attr, *args):
        try:
            return getattr(self.__class__, attr, *args)
        except AttributeError:
            return getattr(self.get_query_set(), attr, *args)