Django models inheritance and Meta class - django

Question

I have a problem with django models inheritance. This is what I have :
class Room(models.Model):
name = models.CharField(max_length=32)
class Container(models.Model):
size = models.IntegerField(default=10)
...
class BigBox(Container):
room = models.ForeignKey(Room)
...
class SmallBox(Container):
big_box = models.ForeignKey(BigBox)
...
class Stuff(models.Model):
container = models.ForeignKey(Container)
...
class Meta:
ordering = ('container__???__name',)
So, with this, I'm able to put some stuff in the big box or in a small box, which is in the big box.
How can I know the type of my stuff field ´container´ in order to acces to the name of the room ? I know I can write
container__big_box__room__name
and
container__room__name
but I would like something like
container__get_room__name.
Is it possible ?
Thank you,
Alex.

Answer 1

To your actual quuestion about the ordering meta, my answer is: I don't think that is possible.
Now, some workarounds:
I would rethink your model hierarchy.
To me a box/container which can be cointained in another box/container is still a box.
Have a look at this alternative:
class Container(models.Model):
size = models.IntegerField(default=10)
room = models.ForeignKey(Room)
...
class ContainableContainer(Container):
parent_container = models.ForeignKey('self', null=True)
...
class Stuff(models.Model):
container = models.ForeignKey(Container)
...
class Meta:
ordering = ('container__room__name',)
With this solution you don't really need a different model, they're both containers, where a cointainer of the cointainer is optional. And so, you can do the ordering as you have already thought.
You would have to be careful with the room field management. You need to make each contained container room be equal with its container's room.
For example, override the save method or use a pre_save signal:
class ContainableContainer(Container):
parent_container = models.ForeignKey('self', null=True)
...
def save(self, *args, **kwargs):
self.room = self.parent_container.room
super(ContainableContainer, self).save(*args, **kwargs)
EDIT: This is actually a tree-like hierarchy. To make it more efficient query-wise django-mptt would be a nice choice.
It allows you to obtain the root container or to iterate over the box hierarchy with more efficient queries.
I don't have any experience with it, but it really seems the best possible solution.