On Thu, Jul 14, 2011 at 10:56 AM, zdenulo <zden...@gmail.com> wrote:
> Greetings to everybody,
> I have a problem for which I didn't find solution on internet,
> therefore I am posting context:
>
> simplified models.py for application testapp (django 1.3):
>
> class Menu(models.Model):
> parent_menu = models.ForeignKey('Menu', blank=True, null=True)
ForeignKeys to themselves should use 'self' as the target model, eg:
parent_menu = models.ForeignKey('self', blank=True, null=True)
> title = models.CharField(max_length=30)
> def __unicode__(self):
> return self.title
>
> class Page(models.Model):
> menu = models.ForeignKey('Menu', blank = True, null=True)
>
>
> file admin.py
>
> from testapp.models import Page, Menu
> from django.contrib import admin
>
> class PageAdmin(admin.ModelAdmin):
> def formfield_for_foreignkey(self, db_field, request, **kwargs):
> if db_field.name == "menu":
> kwargs["queryset"] = Menu.objects.raw('select * from
> testapp_menu where not id in (select distinct parent_menu_id from
> testapp_menu where parent_menu_id is not null)')
> kwargs["queryset"].all = kwargs["queryset"].__iter__
> return super(PageAdmin,
> self).formfield_for_foreignkey(db_field, request, **kwargs)
That just made me weep.
>
>
> class MenuAdmin(admin.ModelAdmin):
> pass
>
> admin.site.register(Menu, MenuAdmin)
> admin.site.register(Page, PageAdmin)
>
> some explanation:
> When I am creating Page, I want to have in a list all Menu instances
> which either don't have parent menu or don't have "child
> menu" (inverse relationship as defined in model). Now I didn't find
> any suitable query using Django syntax, that's why I used raw query.
> It filters Menu objects as I expect, but when I want to save Page
> instance, I get following error 'RawQuerySet' object has no attribute
> 'get'
>
> problem is in method \django\forms\models.py to_python
> 972. value = self.queryset.get(**{key: value})
>
> I don't know how to bypass this error and I didn't find anywhere
> discussion about this case, so every help and advice is much
> appreciated.
>
Don't do crazy monkey patching of queryset classes?
Your query is quite expressible in the ORM:
p_menu_ids =
Menu.objects.filter(parent_menu__isnull=False).order_by('parent_menu').distinct().values_list('parent_menu')
qs = Menu.objects.exclude(id__in=p_menu_ids)
Cheers
Tom
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