[Django]-Can a generic.GenericForeignKey() field be Null?

by

34👍

✅

Perhaps you need to set null=True on the underlying content_type and object_id fields that make up the generic foreign key.

👤Daniel Roseman

54👍

For the lazy/pragmatic:

class MyModel(models.Model):
    ...other fields...
    content_type = models.ForeignKey(ContentType, blank=True, null=True, on_delete=models.SET_NULL)
    object_id = models.PositiveIntegerField(blank=True, null=True)
    content_object = generic.GenericForeignKey('content_type', 'object_id')
👤Mark Chackerian

-3👍

Have you tried setting null=True on the GenericForeignKey? Generic foreign keys aren’t a concept that is recognised by the low-level database application (i.e. MySQL, SQLite, etc.) so you should be able to specify that the field be null.

null=True on a database field in Django signifies that the database field representing that data is allowed to be empty, whereas blank=True tells the Django forms/model validation that the field is OK to be left empty by the user (or you, through the admin interface). Therefore, you might need to use both to achieve what you’re after.

👤Rob Golding

Leave a comment