Return 在多对多关系中代理 class，Django 2.0

Question

从另一个安装的应用程序，我有这样的模型

class Organization(model.Model):
    name = models.CharField(max_length=255, blank=True)

class Person(model.Model):
    name = models.CharField(max_length=255, blank=True)

class Membership(model.Model):

    organization = models.ForeignKey(
        Organization,
        related_name='memberships',
        # memberships will go away if the org does
        on_delete=models.CASCADE,
        help_text="A link to the Organization in which the Person is a member.")

    person = models.ForeignKey(
        Person,
        related_name='memberships',
        null=True,
        # Membership will just unlink if the person goes away
        on_delete=models.SET_NULL,
        help_text="A link to the Person that is a member of the Organization.")

在我的应用程序中，我需要为某些模型添加一些方法。所以我有一个像

这样的模型

class ProxiedOrganization(other_app.models.Organization):
    class Meta:
        proxy = True

    special_attribute = 'foo'


class ProxiedPerson(other_app.models.Person):
    class Meta:
        proxy = True

    def special_method(self):
         print('I do something special')

当我从一个组织获得成员身份时，它们的类型是 other_app.models.Person。

> type(proxied_org_instance.memberships[0].person)
<class 'other_app.models.Person'>

但是，我希望它们成为我的代理实例 class

> type(proxied_org_instance.memberships[0].person)
<class 'my_app.models.ProxiedPerson'>

有什么好的方法吗？这是我可以用查询管理器做的事情吗？该解决方案必须适用于 Django 2.0。

Answer 1

您需要在 Organization 到 ProxiedPerson 中放置一个外键。例如：

class MemberShip(models.Model):
    person = models.ForeignKey(
        ProxyPerson,
        related_name='memberships',
        null=True,
        # Membership will just unlink if the person goes away
        on_delete=models.SET_NULL,
        help_text="A link to the Person that is a member of the Organization.")

或者您可以通过以下方式获取代理人实例：

proxy_person = ProxyPerson.objects.get(pk=proxied_org_instance.memberships[0].person.pk)

或

proxy_persons = ProxyPerson.objects.filter(
                    pk__in = proxied_org_instance.memberships.all().values_list('person_id')
                )

根据documentation

The MyPerson class operates on the same database table as its parent Person class. In particular, any new instances of Person will also be accessible through MyPerson, and vice-versa

意味着您可以通过 ProxyPerson 实例访问 Person 实例，反之亦然。

Answer 2

我改编了 Matt Schinckel 的 work on overriding proxy model relations, for a solution that will work with Django 2.0 and 2.1. The code is available as a library on pypi。

Return 在多对多关系中代理 class，Django 2.0

Return proxied class in many to many relation, Django 2.0

django

django-models

django-2.0