Django 中的逻辑删除or标记删除or软删除

有时候在开发项目中，对某些数据可能只需要逻辑删除，并不真正的从数据库中删除数据。这时候只需要把继承的 Model 从
from django.db import models
改为
from model_utils.models import SoftDeletableModel 即可，就这么简单！

PS:这是不经意间查看 from django.db import models 的 delete 方法时，突然发现有子类复写该 delete 方法，于是就到 SoftDeletableModel 了，哈哈

from model_utils.models import SoftDeletableModel
class Teacher(SoftDeletableModel):
    id = models.AutoField(primary_key=True)
    name = models.CharField(max_length=20,default='someone')

    create_date = models.DateTimeField(auto_now_add=True)
    update_date = models.DateTimeField(auto_now=True)
    class Meta(object):
        db_table = 'teacher'

    def __unicode__(self):
        return "{0}-{1}".format(self.id, self.name)

DIY: 当然如果想深度定制，可以复写上面的方法！

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

class MySoftDeletableQuerySet(QuerySet):
    def delete(self):
        # 1.如果 obj = Student.objects.get(id=6).delete() 删除, 则是走不到该函数的
        # 2.如果 obj = Student.objects.filter(id=6).delete() 删除, 则才会走到该函数
        print 'In the delete of the MySoftDeletableQuerySet, self = {0}'.format(self)
        self.update(is_deleted=True)


class studentManager(models.Manager):
    _queryset_class = MySoftDeletableQuerySet
    def get_queryset(self):
        return super(studentManager,self).get_queryset().filter(is_deleted=False)


# Create your models here.
class Student(models.Model):
    # MySQL 的表只能有一个自增列，如果你在模板中手动指定了自增列则Django就不在为你创建了，否则会给你自动创建自增列
    gender_choices = Choices(
        (1, "Boy"),
        (2, "Girl")
    )
    id = models.AutoField(primary_key=True)
    name = models.CharField(max_length=20,default='someone')
    # 根据模板生成的数据库表中的该列居然是没有默认值的,这有点出乎意料呀，难道该默认值只在 Django 框架里根据 ORM 操作生成 SQL 才能用到
    gender = models.IntegerField(choices=gender_choices,default=1)
    address = models.CharField(max_length=50,verbose_name='地址')
    comments = models.CharField(max_length=50,verbose_name='备注', default='everything is ok')
    is_deleted = models.BooleanField(default=False)
    create_date = models.DateTimeField(auto_now_add=True)
    update_date = models.DateTimeField(auto_now=True)

    objects = studentManager()

    class Meta(object):
        app_label = 'app01'
        db_table = 'student'

    def __unicode__(self):
        return "{0}-{1}-{2}".format(self.id, self.name, self.address)

    def delete(self, using=None, keep_parents=False):
        # 1.如果 obj = Student.objects.get(id=6).delete() 删除, 则才会走到该函数
        # 2.如果 obj = Student.objects.filter(id=6).delete() 删除, 则是走不到该函数的
        print 'using = {0}, keep_parents = {1}'.format(using, keep_parents)
        self.is_deleted = True
        self.save()