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djangodjango-modelsmany-to-manyuml

How to implement Many to many relation in django when the relation contain attributes?

I'm begginer at django and I knew that you can use ManyToManyField to link two models like author-post user-groups. so I have this relation in my UML UML Example

How can I implement this in my code ? my shot was like this

class User(models.Model):
# user fields

class Group(models.Model):
     # group fields

class GroupMember(models.Model):
    group = models.ForeignKey(Group, on_delete=models.DO_NOTHING, db_index=True)
    user = models.ForeignKey(User, on_delete=models.DO_NOTHING, db_index=True)
    IsAdmin = models.BooleanField(default=False, verbose_name='Est un admin')

    class Meta:
        unique_together = (("group", "user"),)

I want to use ManyToManyFields so I can refer between them (if I haven't IsAdmin field, I don't have to create the third class 'GroupMember')

Solution

  • You can find the example from the official doc: https://docs.djangoproject.com/en/3.0/topics/db/models/#extra-fields-on-many-to-many-relationships

    The intermediate model is associated with the ManyToManyField using the through argument to point to the model that will act as an intermediary.

    The Group class in your model should be like:

    class Group(models.Model):
    # group fields
    # ...
    users = models.ManyToManyField(User, through='GroupMember')