Instance belonging in Django Model Inheritance

December 11, 2021

What is the simpliest way to figure out does notification belong to BaseNotification or to ExtendedNotification?

class User(models.Model):
    pass

class BaseNotification(models.Model):
    user = models.ForeignKey(User, on_delete=models.CASCADE, related_name='notifications')

class ExtendedNotification(BaseNotification):
    pass

# usage
for notification in user.notifications.all():
    # --> here <--

>Solution :

You can distinguish the two by using hasattr(notification, 'extendednotification'). Here’s an example of how to use it with a loop:

for notification in user.notifications.all():
    if hasattr(notification, 'extendednotification'):
        extended_notification = notification.extendednotification
        # do stuff with the extended notification
    else:
        # do stuff with the base notification