How to make recursive ManyToManyField relationships that have extra fields symmetrical in Django?

Question

class Food_Tag(models.Model):
    name = models.CharField(max_length=200)
    related_tags = models.ManyToManyField(\'self\', blank=True, symmetrical=False, through=         


        

Answer 1

To create a symmetrical relationship, you have two options:

1) Create two Tag_Relation objects - one with steak as the source, and another with steak as the target:

>>> steak = Food_Tag.objects.create(name="steak")
>>> meat = Food_Tag.objects.create(name="meat")
>>> r1 = Tag_Relation(source=steak, target=meat, is_a=True)
>>> r1.save()
>>> r2 = Tag_Relation(source=meat, target=steak, has_a=True)
>>> r2.save()
>>> steak.related_tags.all()
[]
>>> meat.related_tags.all()
[

2) Add another ManyToManyField to the Food_Tag model:

class Food_Tag(models.Model):
    name = models.CharField(max_length=200)
    related_source_tags = models.ManyToManyField('self', blank=True, symmetrical=False, through='Tag_Relation', through_fields=('source', 'target'))
    related_target_tags = models.ManyToManyField('self', blank=True, symmetrical=False, through='Tag_Relation', through_fields=('target', 'source'))

class Tag_Relation(models.Model):
    source = models.ForeignKey(Food_Tag, related_name='source_set')
    target = models.ForeignKey(Food_Tag, related_name='target_set')

As a note, I'd try to use something more descriptive than source and target for your through model fields.