Django inlineformset-自定义保存方法

class Invoices(models.Model):
    ...
    sum_w_vat = models.DecimalField(max_digits=7, decimal_places=2, default=0)
    sum_wo_vat = models.DecimalField(max_digits=7, decimal_places=2, default=0)
    sum_discount = models.DecimalField(max_digits=7, decimal_places=2, default=0)
    sum_vat = models.DecimalField(max_digits=7, decimal_places=2, default=0)
    sum_paid = models.DecimalField(max_digits=7, decimal_places=2, default=0)
    ...

class InvoiceItems(models.Model):
    invoice = models.ForeignKey(Invoices)
    quantity = models.DecimalField(max_digits=9, decimal_places=2)
    unit = models.ForeignKey(StocklistUnits, verbose_name=\'Merska enota\')
    price = models.DecimalField(max_digits=9, decimal_places=2)
    vat = models.DecimalField(max_digits=4, decimal_places=3)
    discount = models.DecimalField(max_digits=3, decimal_places=1)
    def save(self, **kwargs):
        self.invoice.sum_w_vat += (self.price * self.quantity * self.vat) * self.discount
        self.invoice.sum_wo_vat += (self.price * self.quantity) * self.discount
        self.invoice.sum_discount += (self.price * self.quantity) * ( self.discount / 100 )
        self.invoice.sum_vat += ((self.price * self.quantity * self.vat) * self.discount) - ((self.price * self.quantity) * self.discount)
        super(InvoicesItems, self).save(**kwargs)

InvoiceItems

def edit(request, id = None):
InvoiceFormSet = inlineformset_factory(Invoices, InvoicesItems)

if id == None:
    initial_data = \'\'
    data = Invoices()
else:
    data = get_object_or_404(Invoices, pk=id)
    initial_data = \'\'

if request.method == \'POST\':
    created_invoice = InvoicesForm(request.POST, instance=data)

    form = InvoiceFormSet(request.POST, instance=data)

    if not form.is_valid() and not created_invoice.is_valid():
        //json err msg
    else:
        created_invoice.save()
        form.save()


    json = simplejson.dumps(response, ensure_ascii=False)
    return HttpResponse(json, mimetype=\"application/json\")
else:
    form = InvoicesForm(instance=data, initial=initial_data)
    form_items = InvoiceFormSet(instance=data)
    c = {\'form\':form, \'form_items\':form_items}
    c.update(csrf(request))
    return render_to_response(\'crud_invoice_edit.html\', c)

InvoiceItems

Invoices