字段定义了与模型“实体”的关系，该模型要么未安装，要么是抽象的

Question

我正在使用 django 模型继承来创建一个实体模型，这样我就可以在对话模型中引用两个外键，因为 entity_1 和 entity_2 可以是个人或企业。但是我不断收到以下错误消息：

api.Conversation.entity_1: (fields.E300) Field defines a relation with model 'Entity', which is either not installed, or is abstract.
api.Conversation.entity_2: (fields.E300) Field defines a relation with model 'Entity', which is either not installed, or is abstract.

这是我目前的代码：

class Entity(models.Model):
    id = models.UUIDField(primary_key=True, default=uuid4, editable=False)

    class Meta:
         abstract = True

 class Person(Entity):
    """
    Person model
    """

    avatar = models.ImageField(upload_to=get_upload_avatar_path, blank=True, null=True, default=None, max_length=255)
    first_name = models.CharField(max_length=255)
    last_name = models.CharField(max_length=255)


class Business(Entity):
    """
    Business model
`   """
    name = models.CharField(max_length=255, null=True, default=None)


class Conversation(models.Model):
    id = models.UUIDField(primary_key=True, default=uuid4, editable=False)
    entity_1 = models.ForeignKey(Entity)
    entity_2 = models.ForeignKey(Entity)

Answer 1

你不能引用抽象类。它不创建数据库表。 https://docs.djangoproject.com/en/1.9/topics/db/models/#abstract-base-classes

您可以使用 GenericForeignKey https://docs.djangoproject.com/en/1.9/ref/contrib/contenttypes/#generic-relations

一个例子：

from django.contrib.contenttypes.fields import GenericForeignKey
from django.contrib.contenttypes.models import ContentType
class Conversation(models.Model):
    entity_one = models.ForeignKey(ContentType,on_delete=models.CASCADE,related_name='entity_one')
    entity_two = models.ForeignKey(ContentType,on_delete=models.CASCADE,related_name='entity_two')
    entity1_id = models.PositiveIntegerField()
    entity2_id = models.PositiveIntegerField()
    entity_1_object = GenericForeignKey('entity_one', 'entity1_id')
    entity_2_object = GenericForeignKey('entity_two', 'entity2_id')