Django: "Fake" multiple inheritance

[mic...@herrmann.io]

Hi all,

suppose I have the following model structure

    from django.db import models

    

    class Place(models.Model):

        name = models.CharField(max_length=50)

    

    class Restaurant(Place):

        ...

    

    class Hotel(Place):

        ...

I already have a Restaurant in my database. This Restaurant is now also becoming a Hotel. I would like to declare this in the database as follows:

    restaurant = Restaurant.objects.get(name='Will soon be a hotel')

    Hotel.objects.create(pk=restaurant.pk)

Is this a safe thing to do?

Thanks,

Michael

[Daniel H]

Hi Michael.

First of all, setting the pk to the pk of a different model will do nothing.

You can do this however, using Foreign Keys

restaurant = models.ForeignKey('Restautant')

Then declare a new hotel object like this:

restaurant = Restaurant.objects.get(name='Will soon be a hotel')

Hotel.objects.create(restaurant=restaurant.pk)

What does the "Place" table represent?

[Michael Herrmann]

Thank you Daniel,

I found another way.

Best,

Michael

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[gst]

Will you care share it?
I found the question interresting..
Thanks.

[Michael Herrmann]

Hi gst,

Instead of

    class Hotel(Place):

        ...

I ended up with

    class Hotel(object):

        place = models.OneToOneField(Place, primary_key=True)

I used a OneToOneField instead of ForeignKey because there can only be one hotel in a Place.

M

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[James Schneider]

Hi gst,

Instead of

    class Hotel(Place):

        ...

I ended up with

    class Hotel(object):

        place = models.OneToOneField(Place, primary_key=True)

I used a OneToOneField instead of ForeignKey because there can only be one hotel in a Place.

Just to verify, you're not actually inheriting from (object), right? You're using Hotel(models.Model), I hope?

-James 

[Michael Herrmann]

Yes, of course you're right James, sorry. My classes are actually named differently and I was just trying to get the idea across.

M

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[James Schneider]

Just making sure. Good luck!

-James

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