Django 中的邏輯刪除or標記刪除or軟刪除

有時候在開發項目中，對某些數據可能只需要邏輯刪除，並不真正的從數據庫中刪除數據。這時候只需要把繼承的 Model 從
from django.db import models
改爲
from model_utils.models import SoftDeletableModel 即可，就這麼簡單！

PS:這是不經意間查看 from django.db import models 的 delete 方法時，突然發現有子類複寫該 delete 方法，於是就到 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: 當然如果想深度定製，可以複寫上面 SoftDeletableModel （歸檔系統中的用到的版本）中的相關方法！

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

class MySoftDeletableQuerySet(QuerySet):
    def delete(self):
    	# 0.這個 delete 方法和 Model Student 中定義的 delete 方法相呼應
        # 1.如果 obj = Student.objects.get(id=6).delete() 刪除, 則是走不到該函數的
        # 2.如果 obj = Student.objects.filter(id=6).delete() 刪除, 則纔會走到該函數
        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 的表只能有一個自增列，如果你在模板中手動指定了自增列則Django就不在爲你創建了，否則會給你自動創建自增列
    gender_choices = Choices(
        (1, "Boy"),
        (2, "Girl")
    )
    id = models.AutoField(primary_key=True)
    name = models.CharField(max_length=20,default='someone')
    # 根據模板生成的數據庫表中的該列居然是沒有默認值的,這有點出乎意料呀，難道該默認值只在 Django 框架里根據 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='備註', 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):
    	# 0.這個 delete 方法和 MySoftDeletableQuerySet  中定義的 delete 方法相呼應
        # 1.如果 obj = Student.objects.get(id=6).delete() 刪除, 則纔會走到該函數
        # 2.如果 obj = Student.objects.filter(id=6).delete() 刪除, 則是走不到該函數的
        print 'using = {0}, keep_parents = {1}'.format(using, keep_parents)
        self.is_deleted = True
        self.save()