django之自定義軟刪除Model

軟刪除

     簡單的說，就是當執行刪除操作的時候，不正真執行刪除操作，而是在邏輯上刪除一條記錄。這樣做的好處是可以統計數據，可以進行恢復操作等等。

預備知識

Managers

    Managers 是django models 提供的一個用於提供數據庫查詢操作的接口，對於Django應用程序中的每個model都會至少存在一個Manager

    詳細：https://docs.djangoproject.com/en/dev/topics/db/managers/

django實現軟刪除model

firstly，

from django.db import models
from django.db.models.query import QuerySet

# 自定義軟刪除查詢基類
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

secondly，

# 自定義軟刪除抽象基類
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='客戶分類',
                                 db_constraint=False)
    company = models.CharField(max_length=64, verbose_name="公司名稱")