Django从抽象类访问子类项 [英] Django access to subclasses items from abstract class

问题描述

class Animal(models.Model):
    ....
    class Meta:
        abstract = True

class Cat(models.Model, Animal):
    ...

class Dog(models.Model, Animal):
    ....

我想能够返回Animal的所有子类的所有查询的实例。假设我有一个名为 allData 的函数，它返回所有子类查询集的数组/列表。

I want to be able to return all instances of querysets of all the subclasses of Animal. Lets say I have a function called allData which returns an array/list of all the subclasses querysets.

例如：

x = animal.allData()[0] # should return the first element in the array.

我不介意我们这样做，使用模块，如 django- model-utils 。我只是希望能够返回所有的子类查询集。

I don't mind how we do this, using modules like django-model-utils or not. I just want to be able to return all the subclasses querysets.

推荐答案

这在一个查询中是不可能的。您有两个选项，一个用于使用 django-model-utils ，或者您可以使用 django_polymorphic 。

This is not possible in one query. You have two options, one use to use django-model-utils or you can use django_polymorphic.

多形态更适合您的任务，但 django-model-utils 是由django社区的非常杰出的成员制作的，因此有很多好的支持。

Polymorphic is better suited to your task, however django-model-utils is made by a very prominent member of the django community and as such has a lot of good support.

如果我不得不选择，我会选择 django-model-utilts 由于它是由django团队成员制作的，因此将得到支持。多形态由divio支持，Divio是一家在瑞士大量使用django的私人公司。

If I had to choose, I'd choose django-model-utilts since its made by a member of the django team, and thus will be supported. Polymorphic is supported by divio, which is a private company that heavily uses django based in Switzerland.

至于如何选择子类。您需要使用 django-model-utils 做两件事情。首先，您需要将模型中的对象变量更改为 InheritanceManager（）（从文档改编）：

As for how to select Sub-classes. You need to do two things using django-model-utils. Firstly, you need to change the objects variable in your model to InheritanceManager() like so (adapted from docs):

from model_utils.managers import InheritanceManager

class Place(models.Model):
    # ...
    objects = InheritanceManager()

class Restaurant(Place):
    # ...

class Bar(Place):
    # ...

nearby_places = Place.objects.filter(location='here').select_subclasses()
for place in nearby_places:
    # "place" will automatically be an instance of Place, Restaurant, or Bar

上面的代码将返回所有 Bar s和 Restaurant s，因为它使用 select_subclasses 。

The code above will return all Bars and Restaurants because it uses the select_subclasses.

这篇关于Django从抽象类访问子类项的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！