Re: Keeping filters when adding in the admin interface

El día 29 de febrero de 2012 19:04, Marc Aymerich
<glicerinu@gmail.com> escribió:
> On Wed, Feb 29, 2012 at 10:55 PM, Marc Aymerich <glicerinu@gmail.com> wrote:
>> On Wed, Feb 29, 2012 at 8:22 PM, Mauro Sánchez <mauroka@gmail.com> wrote:
>>> Hello, if I have the following Model:
>>>
>>> class A:
>>>    name
>>>
>>> class B:
>>>    name
>>>    a = models.ForeignKey(A)
>>>
>>> class C:
>>>    name
>>>    b = models.ForeignKey(B)
>>>
>>> And let's suppose that in the Admin Site I have a Filter in the C list
>>> that refers to the A model. Is there a way to keep that filter when I
>>> am going to add a new C object and use it to filter the combobox of
>>> the b filed so that it will only show the b objects that are related
>>> to the A model in the filter?
>>> For example:
>>> If the filter I choose points to the id=1 in the A model, the combobox
>>> for the b field when I add a C object only has to show the B objects
>>> that has a = 1
>>>
>>
>> If I understand you righ, it's a bit triky stuff, you have to do two things:
>> 1)  Define a custom add_form and override their __init__ method with
>> something like:
>>  self.fields['b'].queryset = self.fields['b'].queryset.filter(a=a_pk)
>> 2)  Provides the current value of your filter (a_pk) to the defined form on 1)
>>  I think this can be done overriding modeladmin.get_form() method
>> since request is one of their args, so you can extract the value of
>> the filter on the http referer url and provide it to the form that
>> this method creates.
>>
>
> More specifically:
>
> def get_form(self, request, *args **kwargs):
>    form = super(YourModelAdmin, self).get_form(request, *args, **kwargs)
>    a_pk = get_a_pk_from_http_referer(request)
>    form.a_pk = a_pk
>    return form
>
> def __init__(self, *args, **kwargs):
>   super(YourModelForm, self).__init__(*args, **kwargs)
>   self.fields['b'].queryset = self.fields['b'].queryset.filter(a=self.a_pk)
>

Hello Marc,
the filter in the __init__ method works fine. I know this because I
have set a value manually.
But I have a problem when I try to pass the value self.a_pk to the
filter in the queryset defined in the __init__ method. This is the
error I get:

'CForm' object has no attribute 'a_pk'

It's like the form never received this new variable. What can be the
problem here?

Thanks for the help.
Mauro.

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