Many-to-many relationship with 'through' model returning error on migration

Question

I'm trying to implement a system which allows for two Profile model objects to be a part of a Pair model object.

Here is the Profile, followed by a Pair model:

class Profile(models.Model):
    user = models.OneToOneField(settings.AUTH_USER_MODEL,
                                on_delete=models.CASCADE,
                                null=True, blank=True)
    pair = models.ManyToManyField('self', through='Pair',
                                   symmetrical=False,
                                   related_name='pair_to+')

class Pair(models.Model):
    requester = models.ForeignKey(Profile, related_name='pairing_requester')
    accepter = models.ForeignKey(Profile, related_name='pairing_accepter')
    requester_learns = models.CharField(max_length=60, null=True)
    requester_teaches = models.CharField(max_length=60, null=True)  

The relationship between profiles should be symmetrical, such that (profile1, profile2) are a unique object and I should not expect a (profile2, profile1) to be created.

So, per this article, I am trying to create the relationship.

Upon makemigrations, I am receiving the error:

ERRORS:
<function ManyToManyField.contribute_to_class.<locals>.resolve_through_model at 0x1044b47b8>: (models.E022) <function ManyToManyField.contribute_to_class.<locals>.resolve_through_model at 0x1044b47b8> contains a lazy reference to user_profile.pair, but app 'user_profile' doesn't provide model 'pair'.
user_profile.Profile.pair: (fields.E331) Field specifies a many-to-many relation through model 'Pair', which has not been installed.

What am I doing wrong?

Answer 1

class Pair(models.Model):
    requester = models.ForeignKey(Profile, related_name='pairing_requester')
    accepter = models.ForeignKey(Profile, related_name='pairing_accepter')
    requester_learns = models.CharField(max_length=60, null=True)
    requester_teaches = models.CharField(max_length=60, null=True)  

class Profile(models.Model):
    user = models.OneToOneField(settings.AUTH_USER_MODEL,
                                on_delete=models.CASCADE,
                                null=True, blank=True)
    pair = models.ManyToManyField('self', through='Pair',
                                   symmetrical=False,
                                   related_name='pair_to+')

the thing that you are doing wrong is you need to mention the model before calling a relation to another model, django will create PAIR model first then will install model to the other model. so use this and before making migration drop the old migration files