Django 模型继承管理器吗？（我的好像没有）

发布于 2024-08-25 13:13:57 字数 498 浏览 6 评论 0原文

我有 2 个模型：

class A(Model):
    #Some Fields
    objects = ClassAManager()

class B(A):
    #Some B-specific fields

我希望 B.objects 能够让我访问 ClassAManager 的实例，但事实并非如此......

>>> A.objects
<app.managers.ClassAManager object at 0x103f8f290>
>>> B.objects
<django.db.models.manager.Manager object at 0x103f94790>

为什么不< code>B 继承了 A 的 objects 属性？

原文

I have 2 models:

class A(Model):
    #Some Fields
    objects = ClassAManager()

class B(A):
    #Some B-specific fields

I would expect B.objects to give me access to an instance of ClassAManager, but this is not the case....

>>> A.objects
<app.managers.ClassAManager object at 0x103f8f290>
>>> B.objects
<django.db.models.manager.Manager object at 0x103f94790>

Why doesn't B inherit the objects attribute from A?

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怪我太投入 2024-09-01 13:13:57

您的基类需要是一个抽象基类，以便继承自定义管理器，如所述此处

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吻安 2024-09-01 13:13:57

从 Django 3.1 开始，自定义管理器是从父抽象基类继承的。然而，有一个非常重要的警告 - 与普通类不同，子类不会有默认的对象管理器。您必须在父抽象基类上显式设置它。

例如，这不会工作，

class AbstractBase(Model):
   # child fields come here

   custom_manager = MyCustomManager()

class Child(AbstractBase):
    # child fields come here
    pass

Child.objects.filter(id=1)

您将收到此错误：

> Traceback (most recent call last):
  File "<console>", line 1, in <module>
AttributeError: type object 'Child' has no attribute 'objects'

现在 Child 类只有 1 个管理器 custom_manager，它成为其默认管理器。如果您希望将 objects 作为其默认管理器，那么您必须在父抽象基类上显式声明它。

from django.db.models import Manager, Model

class AbstractBase(Model):
   # child fields come here

   objects = Manager()
   custom_manager = MyCustomManager()

As of Django 3.1, custom managers are inherited from the parent abstract base class. However there is a very important caveat - Unlike in normal classes, the child classes won't have the default objects manager. You will have to explicity set this on the parent abstract base class.

For example, this won't work

class AbstractBase(Model):
   # child fields come here

   custom_manager = MyCustomManager()

class Child(AbstractBase):
    # child fields come here
    pass

Child.objects.filter(id=1)

You will get this error:

> Traceback (most recent call last):
  File "<console>", line 1, in <module>
AttributeError: type object 'Child' has no attribute 'objects'

Now the Child class only has 1 manager custom_manager, which becomes its default manager. If you would like to have objects as its default manager then you will have to explicitly declare this on the parent abstract base class.

from django.db.models import Manager, Model

class AbstractBase(Model):
   # child fields come here

   objects = Manager()
   custom_manager = MyCustomManager()

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