django model meta类定义abstract = True

最新推荐文章于 2025-01-08 16:56:26 发布

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本文介绍了一个抽象基类模型TimeStampedModel的实现方法，该模型提供了自动更新的`created`和`modified`字段。通过Flavor类的具体实现案例，探讨了具体继承与抽象基类在Django中的使用方式及注意事项。

class TimeStampedModel(models.Model):
"""
An abstract base class model that provides selfupdating
``created`` and ``modified`` fields.
"""
created = models.DateTimeField(auto_now_add=True)
modified = models.DateTimeField(auto_now=True)
class Meta:

abstract = True

子类继承 TimeStampedModel

from core.models import TimeStampedModel
class Flavor(TimeStampedModel):
title = models.CharField(max_length=200)

运行migrate时，只会创建一个table Flavor；如果TimeStampedModel不是table ，那么运行migrate时，将会创建2个table；而且Flavor不会有父类TimeStampedModel的created 和modified 字段，需要通过外键关联；而且操作Flavor实例的时候，也会影响TimeStampedModel表

但是注意一点：

concrete inheritance has the potential to become a nasty performance bottleneck. This is even more true when you subclass a concrete model class multiple times.
Further reading:
http://2scoops.co/1.8-model-inheritance