Django笔记 Model的继承和操作

本文介绍，Django中的Model的继承和如何操作数据。

参考
http://charlesleifer.com/blog/django-patterns-model-inheritance/
https://godjango.com/blog/django-abstract-base-class-multi-table-inheritance/

例1.继承 创建 数据

import datetime
from django.db import models, IntegrityError, transaction
from django.template.defaultfilters import slugify

class TitleSlugModel(models.Model):
    # everything the same as above

    def save(self, *args, **kwargs):
        print 'title slug model save() called'

        # ... same as above except adding a "print" statement at the top
        # of the method


class DateAwareModel(models.Model):
    pub_date = models.DateTimeField()
    modified_date = models.DateTimeField()
    created_date = models.DateTimeField()

    class Meta:
        abstract = True

    def save(self, *args, **kwargs):
        print 'date aware model save() called'

        if not self.pk:
            self.created_date = datetime.datetime.now()
        self.modified_date = datetime.datetime.now()

        return super(DateAwareModel, self).save(*args, **kwargs)


class ContentObject(TitleSlugModel, DateAwareModel):
    content = models.TextField()

    def save(self, *args, **kwargs):
        print 'content model save() called'
        super(ContentObject, self).save(*args, **kwargs)

>>> import datetime
>>> from media.models import *
>>> content_obj = ContentObject(title='testing')
>>> content_obj.pub_date = datetime.datetime(2010, 10, 9)
>>> content_obj.save()
content model save() called
title slug model save() called
date aware model save() called

>>> content_obj.modified_date
datetime.datetime(2010, 10, 9, 13, 31, 57, 782511)

>>> content_obj.slug
u'testing'

例2.从子类获取父类

定义继承关系

class Ticket(models.Model):
    title = models.CharField(max_length=255, blank=True)
    description = models.TextField(blank=True)
    name = models.CharField(max_length=255, blank=True)

class InternalTicket(Ticket):
    user = models.ForeignKey('auth.User', null=True)

class CustomerTicket(Ticket):
    product = models.TextField(blank=True)

产生数据

In [1]: CustomerTicket.objects.create(product='Videos', title='Odd Playback', description='doesnt play back fast enough', name='Jane Smith')
Out[1]: <CustomerTicket: CustomerTicket object>


In [2]: Ticket.objects.all()
Out[2]: [<Ticket: Ticket object>]


In [3]: ticket = Ticket.objects.get()

In [4]: ticket.customerticket
Out[4]: <CustomerTicket: CustomerTicket object>


In [5]: ticket.customerticket.product
Out[5]: 'Videos'

In [6]: ticket.description
Out[6]: 'doesnt play back fast enough'

获取数据

n [1]: customer = CustomerTicket.objects.get()

In [2]: customer.description
Out[2]: 'doesnt play back fast enough'


In [3]: customer.ticket_ptr
Out[3]: <Ticket: Ticket object>


In [4]: customer.ticket_ptr_id
Out[4]: 1