如何在Django中扩展管理器方法？

Question

I would like to extend _filter_or_exclude method on my manager, but for some reason, the method is never called.

What I want to achieve is to implicitly filter models, which don't have field deleted = 0 (with all get() and filter() and all() and exclude() and possibly other methods)

My models

from django.db.models import Model, Manager, Q, QuerySet


class BaseManager(Manager):

    def _filter_or_exclude(self, *args, get_deleted=False,  **kwargs):
        clone = super()._filter_or_exclude(*args, **kwargs)
        if not get_deleted:
            clone.query.add(Q(deleted=0))
        return clone

# Just for sure, I extended the method on a querySet as well
class BaseQuerySet(QuerySet):

    def _filter_or_exclude(self, *args, get_deleted=False, **kwargs):
        clone = super()._filter_or_exclude(*args, **kwargs)
        if not get_deleted:
            clone.query.add(Q(deleted=0))
        return clone


class BaseModel(Model):
    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
    deleted = models.IntegerField(default=0)

    ...

    objects = BaseManager.from_queryset(BaseQuerySet)

    class Meta:
        abstract = True

    def delete(self, from_db=False, using=None, keep_parents=False):    
        if from_db:
            super().delete(using, keep_parents)
            return
        self.deleted = 1
        self.save()

class Operation(BaseModel):

    ...

Now when I run

Operation.objects.get(id="...")

The extended method _filter_or_exclude is not called on the custom manager, but on a default one.

What am I doing wrong?

Answer 1

You can override get_queryset method for manager. And to add all instances including deleted ones, you can add another method. like this.

class BaseManager(Manager):
        def get_queryset(self):
            qs = super().get_queryset()
            qs = qs.filter(deleted=1) # or whatever your condition is
            return qs

    def all_objects(self):
        return super().get_queryset()

And use it like this.

Model.objects.get() # filtered results
Model.objects.all_objects.get() # include deleted ones.