How do I filter a field inside of an Inline using a form with a queryset that depends on the instance?

Using Django The Admin
1

Hello!

I’m on django 1.11. I’m having a small issue here when trying to edit the init of a ModelForm, for using in the django admin. If I do something like this:

class SubscriptionAdminForm(forms.ModelForm):
    def __init__(self, *args, **kwargs):
        super(SubscriptionAdminForm, self).__init__(*args, **kwargs)
        print self.fields
        self.fields['billing_address'].queryset = Address.objects.filter(
            contact__pk=self.instance.contact.id)

I have no issues at all, the idea is to filter the Address objects on my Subscription model, so only the Addresses for that subscription appear on a select box. The problem starts when I want to add this form to an Inline!. I have a model called SubscriptionProduct that will contain a Subscritpion and an Address object. Whenever I’ll try something like this:

class SubscriptionProductForm(forms.ModelForm):
    def __init__(self, *args, **kwargs):
        super(SubscriptionProductForm, self).__init__(*args, **kwargs)
        self.fields['address'].queryset = Address.objects.filter(
            contact__pk=self.instance.subscription.contact.id)

    class Meta:
        model = SubscriptionProduct
        fields = '__all__'

It will tell me that:

RelatedObjectDoesNotExist at /blahblah/core/subscription/***/change/
SubscriptionProduct has no subscription.

Which of course it’s not true. SubscriptionProduct does have a subscription. If I use the same form on the ModelAdmin outside of the inline I won’t have this issue.

I’ve also noticed that this doesn’t happen when I try to use some hardcoded values to build my queryset, for instance if I did something like:

self.fields['address'].queryset = Address.objects.filter(
            contact__pk=self.instance.subscription.contact.id)

It would work like a charm.

Can anyone help me trying to make this work? I’ve tried thousand of things and I’m running out of ideas! Maybe someone recognizes this as a known programming mistake.

Thank you!

2

Update: My problem seems to be because the “extra” inlines have no instance, and therefore I have no idea how to get the right “subscription” object for them to be filtered.

3

Could solve it using various stackoverflow posts, will post the code here if anyone needs it in the future. In my TabularInline (admin.py) I added this code. The first function gets the parent object, the second function changes the field:

def get_parent_object_from_request(self, request):
    """
    Returns the parent object from the request or None.
    Note that this only works for Inlines, because the `parent_model`
    is not available in the regular admin.ModelAdmin as an attribute.
    """
    resolved = resolve(request.path_info)
    if resolved.args:
        return self.parent_model.objects.get(pk=resolved.args[0])
    return None

def formfield_for_foreignkey(self, db_field, request=None, **kwargs):
    field = super(SubscriptionProductInline, self).formfield_for_foreignkey(
        db_field, request, **kwargs)
    if db_field.name == 'address':
        if request:
            contact = self.get_parent_object_from_request(request).contact
            field.queryset = field.queryset.filter(contact=contact)
    return field
1 Like
4

Hi @virusereturns thanks for the code !

Do you have the full code ? I don’t understand how the methods are called in the Inline.

(Trying to do something similar)

Thanks !