从父类获取所有子模型-Django [英] Get all children models from a parent class - Django

问题描述

如何从家长班获得所有孩子的模特儿？
例如，我有：

How can I get all the children models from a parent class? As an example I have :

class Device(PolymorphicModel):
   .....

class Mobile(Device): 
   .....

class Computer(Device):
   .....

所以我想从Device模型中获取其所有后代：移动，计算机，而不是实例。

So I want to get from the Device model its all descendants : Mobile, Computer as classes not as instances.

谢谢。

推荐答案

您可以获取 direct 具有 class .__ subclasses__的子类（） [Python-doc] 方法：

You can get the direct subclasses with the class.__subclasses__() [Python-doc] method:

>>> Device.__subclasses__()
[<class 'Mobile'>, <class 'Computer'>]

但是这些也可能具有子类。我们可以开发一种算法，每次获得下一代算法，并一直这样做直到找到新的子类为止，例如：

It is however possible that these also have subclasses. We can develop an algorithm that each time obtains the next generation, and keeps doing this until no new subclasses are found, like:

def get_descendants(klass):
    gen = { klass }
    desc = set()
    while gen:
        gen = { skls for kls in gen for skls in kls.__subclasses__() }
        desc.update(gen)
    return desc

或带有可变参数数量：

def get_descendants(*klass):
    gen = { *klass }
    desc = set()
    while gen:
        gen = { skls for kls in gen for skls in kls.__subclasses__() }
        desc.update(gen)
    return desc

这将返回包含所有内容的 set（）后代（直接和间接）。

this will return a set() containing all descendants (both direct and indirect).

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