How to define a string method for a many to many relation in Django?

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It is possible to define a __str__ method on a model:

class Person(models.Model):
    name = models.CharField(max_length=40)
    hobbies = models.ManyToManyField(Hobby)

    def __str__(self):
        return self.name

But how to define something like this for an automatically generated table through a ManyToManyField? Objects that represent a relationship between a person and a hobby are written like this:

Person_hobbies object (1)

Note that I am not talking about the Hobby object itself, but the object that represents the relation between a Person and a Hobby.

python-3.x django python
1 Answers

But how to define something like this for an automatically generated table through a ManyToManyField?

You can define the junction table model with the through=… parameter [Django-doc]:

class Person(models.Model):
    name = models.CharField(max_length=40)
    hobbies = models.ManyToManyField(Hobby, through='PersonHobby')

    def __str__(self):
        return self.name

class PersonHobby(models.Model):
    person = models.ForeignKey(Person, on_delete=models.CASCADE)
    hobby = models.ForeignKey(Hobby, on_delete=models.CASCADE)

    def __str__(self):
        return f'A string with the {self.person} and the {self.hobby}'

Migrating to a junction model for a ManyToManyField is however not that easy. If it is possible, I would delete migrations that include the ManyToManyField and recreate a migration.

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