返回代理类中的多对多关系,Django 2.0

2023年8月29日 213次阅读

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.所以我有一个类似的模型

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')

当我从组织获得成员资格时,它们的类型为other_app.models.Person.

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

但是,我希望它们是我的代理类的实例

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

有这样做的好方法吗？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.

最佳答案 您需要将组织中的ForeignKey放入ProxiedPerson.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)

要么

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

按照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

表示您可以通过ProxyPerson Instance访问Person Instance,反之亦然.

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