Define an attribute in a model, like an object of the other model in Django

Question

Is posible to define an attribute in a data model like an object of other data model in Django? This is the scenary:

models.py

class Inmueble(models.Model):
    calle = models.CharField(max_length=20, verbose_name="Calle")
    numero = models.CharField(max_length=6, verbose_name="Numero")
    piso = models.IntegerField(verbose_name="Piso", blank=True, null=True)
    galeria_id = models.OneToOneField(Galeria, verbose_name="Galería del Inmueble")


class Galeria(Gallery):
    nombre = models.CharField(max_length=30, verbose_name="Nombre")

The point is: I need to create a new Galeria object automatically every time an Inmueble object is created. Thanks in advance!

                                 Analía.

Answer 1

Maybe AutoOneToOneField is the answer.

Answer 2

There are two ways to handle this:

1. Override the save() method for the Inmueble model.
2. Create a signal handler on Galeria that receives signals emitted by Inmueble

Both methods would work and are acceptable, however I recommend using a signal for a couple reasons:

• It's a bit more de-coupled. If later you change or remove Galeria, your code doesn't break
• The signal handler for postsave includes a boolean value to indicate whether the model is being created or not. You could technically implement the same functionality in model save() by checking if the model has a .id set or not, but IMO the signal is a cleaner solution.

Here's an idea of the code for both of these...

Using a Signal (recommended)

from django.db.models.signals import post_save
from wherever.models import Inmueble

class Galeria(Gallery):
    # ...

def inmueble_postsave(sender, instance, created, **kwargs):
    if created:
        instance.galeria_id = Galeria.objects.create()
        instance.save()

post_save.connect(inmueble_postsave, sender=Inmueble, dispatch_uid='galeria.inmueble_postsave')

Overriding Model save() Method

from wherever.models import Galeria

class Inmueble(models.Model):

    # ...

    def save(self, force_insert=False, force_update=False):
        # No Id = newly created model
        if not self.id:
            self.galeria_id = Galeria.objects.create()
            super(Inmueble, self).save()

Answer 3

Thank you very much for resolve my concerns. Finally, I did:

from django.db.models.signals import post_save

class Galeria(Gallery):

  inmueble_id = models.ForeignKey(Inmueble)

  def inmueble_postsave(sender, instance, created, **kwargs):
    if created:
        instance = Galeria.objects.create(inmueble_id=instance,     title=instance.calle+' '+instance.numero, title_slug=instance.calle+' '+instance.numero)     
        instance.save()

  post_save.connect(inmueble_postsave, sender=Inmueble,  dispatch_uid='galeria.inmueble_postsave')

Analía Lorenzatto.