[Django]-Django model inheritance: Create a subclass using existing super class

by

32👍

✅

Multi-table inheritance is just OneToOneField relation between Place and Restaurant. 

place = Place.objects.get(id=1)               

# Create a restaurant using existing Place   
restaurant = Resturant(place_ptr=place)
restaurant.save()
👤Mariusz Jamro

13👍

place = Place.objects.get(id=1)

# Create a restaurant using existing Place
place.__class__ = Restaurant
place.save()
restaurant = place
👤Davide Callegari

9👍

While undocumented, this seems to do the trick:

restaurant(place_ptr=place).save_base(raw=True)

This solves the problem without using any hacks and is the shortest solution, also in terms of processing, using Django APIs.

While searching for this solution, I also found a slightly longer one, but using documented APIs. It is basically the same as Mariusz answer, also see this answer for more details:

from django.forms.models import model_to_dict

restaurant(place_ptr=place, **model_to_dict(place)).save()

However, this second one is more risky due to limited field set returned by the model_to_dict (see again the answer explaining the differences among various methods presented). Naturally, it also generates more DB calls because it writes to both tables.

👤velis

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