With your example, you can also find the records through>>> ted.person_set.all().
On Friday, October 16, 2020 at 7:05:51 PM UTC-4 David Nugent wrote: > This is expected with your code. You've created an asymmetric > relationship from bill to ted, but not the reverse. This would be > appropriate in a "follow" relationship. For symmetric relationships you > need to create records in both directions. There are a few ways to do this > but a helper function on the Person model is the most direct approach, > something along the lines: > > def add_friendship(self, person, symmetric=True): > friendship = Friendship.objects.get_or_create(personA=self, > personB=person) > if symmetric: > # avoid recursion > person.add_friendship(self, False) > return friendship > > > Regards, David > > On 17 Oct 2020, at 05:38, gjgilles via Django users < > django...@googlegroups.com> wrote: > > There are no responses to the same question on stackoverflow, so hopefully > someone here can provide a solution. > <https://stackoverflow.com/questions/64346385/how-to-make-a-recursive-manytomany-relationship-symmetrical-with-django> > > > I've read the docs. > <https://docs.djangoproject.com/en/3.0/ref/models/fields/#django.db.models.ManyToManyField.symmetrical> > I've read this question too, > <https://stackoverflow.com/questions/4129439/how-to-make-recursive-manytomanyfield-relationships-that-have-extra-fields-symme> > but the following code is not working as the Django docs describe. > If *bill* and *ted *are friends,* bill.friends.all() *should include > *ted, *and *ted.friends.all() *should include *bill*. This is not what > Django does. *ted*'s query is empty, while *bill*'s query includes *ted*. > > # people.modelsfrom django.db import models > > class Person(models.Model): > name = models.CharField(max_length=255) > friends = models.ManyToManyField("self", > through='Friendship', > through_fields=('personA', 'personB'), > symmetrical=True, > ) > > def __str__(self): > return self.name > > class Friendship(models.Model): > personA = models.ForeignKey(Person, on_delete=models.CASCADE, > related_name='personA') > personB = models.ForeignKey(Person, on_delete=models.CASCADE, > related_name='personB') > start = models.DateField(null=True, blank=True) > end = models.DateField(null=True, blank=True) > > def __str__(self): > return ' and '.join([str(self.personA), str(self.personB)]) > > > > > >>> import django > >>> django.__version__ > '3.1.2' > >>> from people.models import Person, Friendship>>> bill = > >>> Person(name='bill')>>> bill.save()>>> ted = Person(name='ted')>>> > >>> ted.save()>>> bill_and_ted = Friendship(personA=bill, personB=ted)>>> > >>> bill_and_ted.save()>>> bill.friends.all() > <QuerySet [<Person: ted>]>>>> ted.friends.all() > <QuerySet []>>>> ted.refresh_from_db()>>> ted.friends.all() > <QuerySet []>>>> ted = Person.objects.get(name='ted')>>> ted.friends.all() > <QuerySet []> > > > Can someone please show me how to make this behave as expected. > > > -- > You received this message because you are subscribed to the Google Groups > "Django users" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to django-users...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/django-users/MJmh5Qw--3-2%40tutanota.com > <https://groups.google.com/d/msgid/django-users/MJmh5Qw--3-2%40tutanota.com?utm_medium=email&utm_source=footer> > . > > > -- You received this message because you are subscribed to the Google Groups "Django users" group. To unsubscribe from this group and stop receiving emails from it, send an email to django-users+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/django-users/f1b39d06-6100-4b6c-94a5-1ec60fa45f80n%40googlegroups.com.
