Django: accessing the model instance from within ModelAdmin?

问题

I've got a model for Orders in a webshop application, with an auto-incrementing primary key and a foreign key to itself, since orders can be split into multiple orders, but the relationship to the original order must be maintained.

class Order(models.Model):
    ordernumber = models.AutoField(primary_key=True)
    parent_order = models.ForeignKey('self', null=True, blank=True, related_name='child_orders')
    # .. other fields not relevant here

I've registered an OrderAdmin class for the admin site. For the detail view, I've included parent_order in the fieldsets attribute. Of course, by default this lists all the orders in a select box, but this is not the desired behaviour. Instead, for orders that don't have a parent order (i.e. have not been split from another order; parent_order is NULL/None), no orders should be displayed. For orders that have been split, this should only display the single parent order.

There's a rather new ModelAdmin method available, formfield_for_foreignkey, that seems perfect for this, since the queryset can be filtered inside it. Imagine we're looking at the detail view of order #11234, which has been split from order #11208. The code is below

def formfield_for_foreignkey(self, db_field, request, **kwargs):
    if db_field.name == 'parent_order':
        # kwargs["queryset"] = Order.objects.filter(child_orders__ordernumber__exact=11234)
        return db_field.formfield(**kwargs)
    return super(OrderAdmin, self).formfield_for_foreignkey(db_field, request, **kwargs)

The commented row works when run in a Python shell, returning a single-item queryset containing order #11208 for #11234 and all other orders that may have been split from it.

Of course, we can't hard-code the order number there. We need a reference to the ordernumber field of the order instance whose detail page we're looking at. Like this:

kwargs["queryset"] = Order.objects.filter(child_orders__ordernumber__exact=?????)

I've found no working way to replace ????? with a reference to the "current" Order instance, and I've dug pretty deep. self inside formfield_for_foreignkey refers to the ModelAdmin instance, and while that does have a model attribute, it's not the order model instance (it's a ModelBase reference; self.model() returns an instance, but its ordernumber is None).

One solution might be to pull the order number from request.path (/admin/orders/order/11234/), but that is really ugly. I really wish there is a better way.

回答1:

I think you might need to approach this in a slightly different way - by modifying the ModelForm, rather than the admin class. Something like this:

class OrderForm(forms.ModelForm):

    def __init__(self, *args, **kwargs):
        super(OrderForm, self).__init__(*args, **kwargs)
        self.fields['parent_order'].queryset = Order.objects.filter(
            child_orders__ordernumber__exact=self.instance.pk)

class OrderAdmin(admin.ModelAdmin):
    form = OrderForm

回答2:

I've modeled my inline class this way. It's a bit ugly on how it gets the parent form id to filter inline data, but it works. It filters units by company from the parent form.

~~The original concept is explained here http://www.stereoplex.com/blog/filtering-dropdown-lists-in-the-django-admin~~

class CompanyOccupationInline(admin.TabularInline):

    model = Occupation
    # max_num = 1
    extra = 0
    can_delete = False
    formset = RequiredInlineFormSet

    def formfield_for_dbfield(self, field, **kwargs):

        if field.name == 'unit':
            parent_company = self.get_object(kwargs['request'], Company)
            units = Unit.objects.filter(company=parent_company)
            return forms.ModelChoiceField(queryset=units)
        return super(CompanyOccupationInline, self).formfield_for_dbfield(field, **kwargs)

    def get_object(self, request, model):
        object_id = resolve(request.path).args[0]
        try:
            object_id = int(object_id)
        except ValueError:
            return None
        return model.objects.get(pk=object_id)

回答3:

The above answer from Erwin Julius worked for me, except I found that the name "get_object" conflicts with a Django function so name the function "my_get_object".

class CompanyOccupationInline(admin.TabularInline):

    model = Occupation
    # max_num = 1
    extra = 0
    can_delete = False
    formset = RequiredInlineFormSet

    def formfield_for_dbfield(self, field, **kwargs):

        if field.name == 'unit':
            parent_company = self.my_get_object(kwargs['request'], Company)
            units = Unit.objects.filter(company=parent_company)
            return forms.ModelChoiceField(queryset=units)
        return super(CompanyOccupationInline, self).formfield_for_dbfield(field, **kwargs)

    def my_get_object(self, request, model):
        object_id = request.META['PATH_INFO'].strip('/').split('/')[-1]
        try:
            object_id = int(object_id)
        except ValueError:
            return None
        return model.objects.get(pk=object_id)

It told me not to "respond" to others' answers, but I'm not allowed to "reply" yet, and I have been looking for this for a while so hope this will be helpful to others. I am also not allowed to upvote yet or I totally would!

来源：https://stackoverflow.com/questions/949268/django-accessing-the-model-instance-from-within-modeladmin

标签

django

django-admin

modeladmin