Django, in many to many relationship within the self class, how do I reference each other in terms of ORM?

问题

class User(models.Model):
    name = models.CharField(max_length=100)
    age = models.IntegerField()
    gender = models.IntegerField()
    email = models.CharField(max_length=100)
    password = models.CharField(max_length=255)
    following = models.ManyToManyField("self", related_name='followers')
    objects = UserManager()
    def __repr__(self):
        return "User: {0}".format(self.name)

In my model, User, users can follow and followed by each other.

I can find who the user is following by this:

user1 = User.objects.get(id=1)
following = user1.following.all()

However, I can't figure out how to find whom the user is followed by.

I tried:

user1.followers.all()

since it is the related_name in the following field in my model.

Can anybody please teach me how to do this?

Thank you very much.

回答1:

You should pass the symmetrical attribute to be False.

From the docs:

When Django processes this model, it identifies that it has a ManyToManyField on itself, and as a result, it doesn’t add a followers attribute to the User class. Instead, the ManyToManyField is assumed to be symmetrical – that is, if I am your follower, then you are my follower.

If you do not want symmetry in many-to-many relationships with self, set symmetrical to False. This will force Django to add the descriptor for the reverse relationship, allowing ManyToManyField relationships to be non-symmetrical.

In your case:

class User(models.Model):
    # ...
    following = models.ManyToManyField('self', related_name='followers', symmetrical=False)
    # ...

Then in your views.py you can access both:

following = user.following.all()
followers = user.followers.all()

Since now the relationship with self is non-symmetrical.

来源：https://stackoverflow.com/questions/45847930/django-in-many-to-many-relationship-within-the-self-class-how-do-i-reference-e