from django.db import models
from django.db.models.query import QuerySet
 
# 自定义软删除查询基类
class SoftDeletableQuerySetMixin(object):
  """
  QuerySet for SoftDeletableModel. Instead of removing instance sets
  its ``is_deleted`` field to True.
  """
 
  def delete(self):
    """
    Soft delete objects from queryset (set their ``is_deleted``
    field to True)
    """
    self.update(is_deleted=True)
 
 
class SoftDeletableQuerySet(SoftDeletableQuerySetMixin, QuerySet):
  pass
 
 
class SoftDeletableManagerMixin(object):
  """
  Manager that limits the queryset by default to show only not deleted
  instances of model.
  """
  _queryset_class = SoftDeletableQuerySet
 
  def get_queryset(self):
    """
    Return queryset limited to not deleted entries.
    """
    kwargs = {'model': self.model, 'using': self._db}
    if hasattr(self, '_hints'):
      kwargs['hints'] = self._hints
 
    return self._queryset_class(**kwargs).filter(is_deleted=False)
 
 
class SoftDeletableManager(SoftDeletableManagerMixin, models.Manager):
  pass

# 自定义软删除抽象基类
class SoftDeletableModel(models.Model):
  """
  An abstract base class model with a ``is_deleted`` field that
  marks entries that are not going to be used anymore, but are
  kept in db for any reason.
  Default manager returns only not-deleted entries.
  """
  is_deleted = models.BooleanField(default=False)
 
  class Meta:
    abstract = True
 
  objects = SoftDeletableManager()
 
  def delete(self, using=None, soft=True, *args, **kwargs):
    """
    Soft delete object (set its ``is_deleted`` field to True).
    Actually delete object if setting ``soft`` to False.
    """
    if soft:
      self.is_deleted = True
      self.save(using=using)
    else:
      return super(SoftDeletableModel, self).delete(using=using, *args, **kwargs)
 
class CustomerInfo(SoftDeletableModel):
  nid = models.AutoField(primary_key=True)
  category = models.ForeignKey("CustomerCategory", to_field="nid", on_delete=models.CASCADE, verbose_name='客户分类',
                 db_constraint=False)
  company = models.CharField(max_length=64, verbose_name="公司名称")