How do I make many-to-many field optional in Django?

django django-admin many-to-many

When you have a many-to-many relationship (related_name, not through) and you are trying to use the admin interface you are required to enter one of the relationships even though it does not have to exist for you to create the first entry.

I'm creating an app that is an event organizer. Imagine we had Event and Group models, bound with many-to-many relationship.

Django related_name creates another table with the indices of the two other tables.
But I see no reason why this extra table has to be populated.

If I work with the database through phpMyAdmin I can create a Group without registering an Event, since the connection between the two is only through a separate table, and there is no database value enforcement at given level.

How do I make the admin interface this realize it? How do I make the many-to-many field optional in Django?

Ludwik Trammer

If you want to be able to specify ManyToMany relation without making it required just use blank=True:

class Group(models.Model):
    ...
    events = models.ManyToManyField(Event, blank=True)

This does solve the problem. Using the blank was not as obvious to me because I thought the manytomany created a table that links the events with the groups (events = models.ManyToManyField(Event, related_name="groups", blank=True) So it was not clear to use the blank since Event is not actually a field in the group table. Anyway it worked so thank you!!!

@omouse I think yes, blank is for django validation, and null for the database. In this kind of case (like for IntegerField) it makes no sense to put one without the other I think

Do you really need to have null=True? I was under the impression null doesn't have any affect on ManyToMany fields: stackoverflow.com/questions/18243039/…

Yeah, um @TylerHayes is right. null=True is basically a no-op and is nonsensical in the context of a ManyToMany. I'm open to being shown how I'm mistaken.

null=True is not required, at least from Django 1.5 onwards.

How do I make many-to-many field optional in Django?

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