用于反向外键查找的 Django 自定义管理器（相关管理器）答案

【问题标题】：Django Custom Manager for Reverse Foreignkey Lookup (Related Manager)用于反向外键查找的 Django 自定义管理器（相关管理器）
【发布时间】：2020-04-02 13:53:08
【问题描述】：

我正在使用自定义模型管理器进行软删除，并希望进行反向外键查找（相关管理器）。

经理：

class SoftDeletionQuerySet(QuerySet):
    def delete(self):
        return super(SoftDeletionQuerySet, self).update(deleted_at=timezone.now())

    def hard_delete(self):
        return super(SoftDeletionQuerySet, self).delete()

    def alive(self):
        return self.filter(deleted_at=None)

    def dead(self):
        return self.exclude(deleted_at=None)


class SoftDeletionManager(models.Manager):
    use_for_related_fields = True

    def __init__(self, *args, **kwargs):
        self.status = kwargs.pop("status", "all")
        super(SoftDeletionManager, self).__init__(*args, **kwargs)

    def get_queryset(self):
        if self.status == "alive":
            return SoftDeletionQuerySet(self.model).filter(deleted_at=None)
        elif self.status == "dead":
            return SoftDeletionQuerySet(self.model).exclude(deleted_at=None)
        else:
            return SoftDeletionQuerySet(self.model)

    def hard_delete(self):
        return self.get_queryset().hard_delete()



class SoftDeletionModel(models.Model):
    deleted_at = models.DateTimeField(blank=True, null=True)

    objects = SoftDeletionManager(status="alive")
    dead_objects = SoftDeletionManager(status="dead")
    all_objects = SoftDeletionManager()

    class Meta:
        abstract = True

    def delete(self):
        self.deleted_at = timezone.now()
        self.save()

    def hard_delete(self):
        super(SoftDeletionModel, self).delete()

用于模型：

class Sowi(SoftDeletionModel):
    owner = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)

现在，对于给定的user，我想获得他的user.sowi_set，但只有那些“活着”的 SoWi。 “正常”user.sowi_set 还返回已死的元素，即具有deleted_at 值！= 无。如何只获取活动对象？

提前致谢！

【问题讨论】：

标签： python django django-models django-views

【解决方案1】：

当user.sowi_set.all()被调用时，你的管理器会被django自动初始化，参数为空。为了解决这个问题，我在django初始化manager时寻找了传递参数的方法。然后，我找到了this question。

您必须像这样更改代码。

def manager_factory(status=None):
    class SoftDeletionManager(models.Manager):
        deletion_status = status
        use_for_related_fields = True

        def get_queryset(self):
            if self.deletion_status == "alive":
                return SoftDeletionQuerySet(self.model).filter(deleted_at=None)
            elif self.deletion_status == "dead":
                return SoftDeletionQuerySet(self.model).exclude(deleted_at=None)
            else:
                return SoftDeletionQuerySet(self.model)

        def hard_delete(self):
            return self.get_queryset().hard_delete()
    return SoftDeletionManager()


class SoftDeletionModel(models.Model):
    deleted_at = models.DateTimeField(blank=True, null=True)

    objects = manager_factory("alive")
    dead_objects = manager_factory("dead")
    all_objects = manager_factory()

    class Meta:
        abstract = True

    def delete(self):
        self.deleted_at = timezone.now()
        self.save()

    def hard_delete(self):
        super(SoftDeletionModel, self).delete()

【讨论】：