您好, 欢迎来到 !    登录 | 注册 | | 设为首页 | 收藏本站

与Django中抽象模型相关的ForeignKey字段

与Django中抽象模型相关的ForeignKey字段

在Django中无法将外键安装到抽象模型。但是,您可以将外键安装到非抽象基类。唯一的限制是反向外键关系将返回基类实例。您可以使用django- polymorphic来规避此限制。

Django Polymorphic允许您查询基类对象,但可以检索子类实例

>>> Project.objects.create(topic="Department Party")
>>> ArtProject.objects.create(topic="Painting with Tim", artist="T. Turner")
>>> ResearchProject.objects.create(topic="Swallow Aerodynamics", supervisor="Dr. Winter")

>>> Project.objects.all()
[ <Project:         id 1, topic "Department Party">,
  <ArtProject:      id 2, topic "Painting with Tim", artist "T. Turner">,
  <ResearchProject: id 3, topic "Swallow Aerodynamics", supervisor "Dr. Winter"> ]

要使用django多态,只需要声明以Polymorphic Model为基类的模型即可:

from django.db import models
from polymorphic.models import PolymorphicModel

class ModelA(PolymorphicModel):
    field1 = models.CharField(max_length=10)

class ModelB(ModelA):
    field2 = models.CharField(max_length=10)

class ModelC(ModelB):
    field3 = models.CharField(max_length=10)

外键还将返回子类实例,这是您需要的:

# The model holding the relation may be any kind of model, polymorphic or not
class RelatingModel(models.Model):
    many2many = models.ManyToManyField('ModelA')  # ManyToMany relation to a polymorphic model

>>> o=RelatingModel.objects.create()
>>> o.many2many.add(ModelA.objects.get(id=1))
>>> o.many2many.add(ModelB.objects.get(id=2))
>>> o.many2many.add(ModelC.objects.get(id=3))

>>> o.many2many.all()
[ <ModelA: id 1, field1 (CharField)>,
  <ModelB: id 2, field1 (CharField), field2 (CharField)>,
  <ModelC: id 3, field1 (CharField), field2 (CharField), field3 (CharField)> ]

考虑到这些查询性能稍差一些

Go 2022/1/1 18:48:59 有269人围观

撰写回答


你尚未登录,登录后可以

和开发者交流问题的细节

关注并接收问题和回答的更新提醒

参与内容的编辑和改进,让解决方法与时俱进

请先登录

推荐问题


联系我
置顶