Filtering generic relation with additional field

[guardbadger]

Hi all,

Appreciate some help trying to build a queryset. Im hoping I can make
this in django, without having to crack open raw sql... Here is my
setup:

class Container(models.Model):
permissions = generic.GenericRelation(Permission)

class Item(models.Model):
container = models.ForeignKey(Container)
extraSetting = models.ForeignKey(ExtraSetting)

class Permission(models.Model):
content_type = models.ForeignKey(ContentType)
content_object = generic.GenericForeignKey()
extraSetting = models.ForeignKey(ExtraSetting)

class ExtraSetting(models.Model):
....

Convoluted made up example, but hopefully you can see what the data
might be.

So the problem im trying to solve. I need to get a list of items and
their permissions, but restrict the permission set so that I only get
permissions where extraSetting is the same on the Item and on the
permission.

So I want to run something like

Item.objects.filter(container__permissions__extraSetting=Item.extraSetting)

Hope this makes some form of sense...

thanks

guardbadger

[Michal Petrucha]

What I think you want to use is this: http://django.me/f
In your case something like

Item.objects.filter(container__permissions__extraSetting=F('extraSetting'))

Michal

[Anthony Musaluke]

Hi Michal

I a new to django but have been following the tutorial.

I have a question on your answer: Which file would you place this code in if you wanted to have that filtering visible in the site admin interface. Would you need to create a custom selection field from which you can pick to populate the relevant model field? I am not so sure yet how to tie that in since it looks like its using the DB access API at this stage?

Thanks

Anthony

[kenneth gonsalves]

On Wed, 2011-11-09 at 13:41 +0200, Anthony Musaluke wrote:
> I a new to django but have been following the tutorial. I have a
> question on your answer: Which file would you place this code in if
> you wanted to have that filtering visible in the site admin interface.
> Would you need to create a custom selection field from which you can
> pick to populate the relevant model field? I am not so sure yet how to
> tie that in since it looks like its using the DB access API at this
> stage?

are you referring to this:
https://docs.djangoproject.com/en/1.3/ref/contrib/admin/#django.contrib.admin.ModelAdmin.list_filter

which is normally added to admin.py
--
regards
Kenneth Gonsalves

[Anthony Musaluke]

Almost like that, except lets say you had a field you wanted to use as a list box but its contents depend on what you select in another field. Meaning, you want to use the results of a database query to populate it so you can select an item from the results.

Not sure if my explanation is making sense ;)

Thanks

Anthony

--
regards
Kenneth Gonsalves

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