如何检查 django 模型 ManyToManyField 是对称的，如果对称=假?

Question

我正在尝试在Django中创建一个追随者系统。

follows = models.ManyToManyField('self', related_name='follower', symmetrical=False, null=True, blank=True)

由于系统不应该是对称的，如何检查两个用户是否相互跟随？

如果可能的话，我想在模型中有一个函数。我可能会在另一个字段和其他地方的limit_choices_to中使用此功能。

我最初的想法是添加一个"朋友"字段并使其对称，但这会在以后带来其他问题。

Answer 1

我没有找到一个简单的解决方案，不需要额外的模型。 这是我所做的：

如果您实现了类似CustomUser(AbstractUser)的东西，则不需要创建Person(models.Model)。否则Person类在许多情况下都很有用。

count_函数非常有用，但大多数用例都不需要。

在accounts/models.py里面，我补充说：

RELATIONSHIP_FOLLOWING = 1
RELATIONSHIP_BLOCKED = 2
RELATIONSHIP_STATUSES = (
(RELATIONSHIP_FOLLOWING, 'Following'),
(RELATIONSHIP_BLOCKED, 'Blocked'),
)
class Person(models.Model):
relationships = models.ManyToManyField('self', through='Relationship',
symmetrical=False,
related_name='related_to')
def get_relationships(self, status):
return self.relationships.filter(
to_people__status=status,
to_people__from_person=self)
def get_related_to(self, status):
return self.related_to.filter(
from_people__status=status,
from_people__to_person=self)
def get_following(self):
return self.get_relationships(RELATIONSHIP_FOLLOWING)
def get_followers(self):
return self.get_related_to(RELATIONSHIP_FOLLOWING)
def count_following(self):
return len(self.get_relationships(RELATIONSHIP_FOLLOWING))
def count_followers(self):
return len(self.get_related_to(RELATIONSHIP_FOLLOWING))
def get_friends(self):
return self.relationships.filter(
to_people__status=RELATIONSHIP_FOLLOWING,
to_people__from_person=self,
from_people__status=RELATIONSHIP_FOLLOWING,
from_people__to_person=self)
def count_friends(self):
return len(self.get_friends())
class Relationship(models.Model):
from_person = models.ForeignKey(Person, related_name='from_people', on_delete=models.CASCADE)
to_person = models.ForeignKey(Person, related_name='to_people', on_delete=models.CASCADE)
status = models.IntegerField(choices=RELATIONSHIP_STATUSES)
def add_relationship(self, person, status):
relationship, created = Relationship.objects.get_or_create(
from_person=self,
to_person=person,
status=status)
return relationship
def remove_relationship(self, person, status):
Relationship.objects.filter(
from_person=self,
to_person=person,
status=status).delete()
return