Okay I got it by using QuerySet's API extra() method
http://docs.djangoproject.com/en/dev/ref/models/querysets/
All I wanted after all is to get some fields from one model, get some fields
from some other model (which is related to the first model through a
foreignkey), and show that through the template. I was sure there was some
other fancy way to do this, but I haven't found anything but to inject the raw
SQL statement to add another field (calculated and labeled "descripcion" here
below)
This is how my view looks like now (take a look at the second line, where the
extra() method is used):
def itempedidos(request, a_pedido_nro):
pedidos_available = Pedido.objects.get(id=a_pedido_nro)
items_available = ItemPedido.objects.extra(select={'descripcion':'SELECT
basicservices_consumible.descripcion FROM basicservices_consumible,
basicservices_itempedido WHERE basicservices_consumible.id =
basicservices_itempedido.item_id_id'}).filter(nro_pedido=a_pedido_nro)
mydict = {"pedidos_available":pedidos_available,
"items_available":items_available}
return render_to_response('sidea/itempedidos.html', {'mydict': mydict})
I think this is something rather usual (have fields from 2 different models and
show them together, just a JOIN...).
Thanks
Regards
Mario
________________________________
From: Mario Zorz <marionetaz...@yahoo.com>
To: django-users@googlegroups.com
Sent: Tuesday, March 10, 2009 12:09:03 AM
Subject: Re: creating a join of 2 models in a view, and accessing such an
object collection in a template
On Mon, 2009-03-09 at 10:31:16 PM, Malcolm Tredinnick wrote:
>> Is it possible in a django view, to take objects from 2 different
>> models, which are related one to the other through a ForeignKey
>> (primary key of one model is foreign key in the other model), make
>> something similar to an SQL JOIN and have the collection of these
>> joined instances passed to the template through the render_to_response
>> shortcut? I need to do this specifically to show fields from both
>> models in the same template/view.
>
>This is exactly the situation covered by the tutorial ([1]), where the
>Choice model is relate to the Poll model by a ForeignKey. Displaying
>polls and related choices is covered in part 3, the models are set up in
>part 1.
>
>[1] http://docs.djangoproject.com/en/dev/intro/tutorial01/
>
>You didn't skip doing the tutorial did you?
Hi Malcolm, first of all thanks for your quick response
To be totally honest yes I have read everything but it was several months ago
and now tried to move on from where I was.
However I coudln't help feeling a little embarrassed with your answer so I
carefully went through the Poll/Choice example in the tutorial once more :p
(just kidding)
Getting to the point I think I didn't describe the scenario quite well. Using
the same Poll/Choice example, let's say first I have two models Poll and Choice
(just as in the example).
Now let's say there's a third model called C, to which the Choice model relates
through a ForeignKey as well (so, I modify the Choice model in the examlpe and
make it have a foreign key to Poll as in the example, but now it also has a
foreign key to model C, and we eliminate the "choice" field in the Choice
model). In a more human way, let's say Choices are not just a varchar but can
only be picked from a "list of possible choices" instead (model C). Model C
happens to have a "description" field that will hold the meaning of each
possible "choice" each instance of Choice might be referring to.
Now how can I make a join of C and Choice, so I can iterate through such a
collection and show for each item in it say, fields "description" from model C
as well as field "votes" from model Choice?
What I think I need to do in the view is, pass on to the template a collection
of a new kind of object that will have, for each instance, fields "description"
(from model C), "choice_id" and "votes" (from model Choice).
The question is: what's the best way to accomplish this? I think I'm not
missing anything but in case I do, I apologize and would very much appreciate
it if anyone helps me see the light :)
Thanks a lot
Regards
Mario
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