Django ModelForm-访问表单valid中的自定义字段

我已经添加了一个自定义字段到一个模型表单如下,但我不能访问我的UpdateView字段。我试过打印对象,但字段设备\电路\子网不在其中,在对象外部引用它也会引发错误。

谢谢

表单.py

class SiteServiceForm(forms.ModelForm):
    class Meta:
        model = DeviceCircuitSubnets
        fields = ['device','circuit','subnet','monitored','interface_name','get_bgp','wb_bgp','db_bgp','get_interface','wb_interface','db_interface','get_aws','wb_aws','db_aws']

        def __init__(self, *args, **kwargs):
            self.is_add = kwargs.pop("is_add", False)
            site_id = kwargs.pop("site_id")
            super(SiteServiceForm, self).__init__(*args, **kwargs)
            self.fields['device'].required = False
            self.fields['circuit'].required = False
            self.fields['subnet'].required = False
            self.fields['device_circuit_subnet'] = DeviceCircuitSubnetField(
                    queryset=DeviceCircuitSubnets.objects.filter(device__site_id=site_id).select_related(
                        'device', 'circuit', 'subnet'
                    ),
                    label='Device / Circuit / Subnet'
            )
            self.helper = FormHelper(self)
            self.helper.form_id = 'site_service_form'
            self.helper.form_method = 'POST'
            self.helper.layout = Layout(
                Div(
                    Div(
                        Div(HTML('<i class="fa fa-bolt fa-fw"></i> Service'), css_class='card-header'),
                        Div(
                            Div(    
                                Div(
                                    Field('device_circuit_subnet', css_class='chosen'),

                                css_class='col-lg-6'
                                ),     
                                Div(
    ...

视图.py

class AddSiteService(PermissionRequiredMixin, CreateView):
    form_class = SiteServiceForm
    template_name = "app_settings/tabs_form.html"
    permission_required = 'config.add_device_circuit_subnet'

    def dispatch(self, *args, **kwargs):
        self.site_id = self.kwargs['site_id']
        return super(AddSiteService, self).dispatch(*args, **kwargs)

    def get_success_url(self, **kwargs):         
        return reverse_lazy("config:site_services", args=(self.site_id))

    def get_form_kwargs(self, *args, **kwargs):
        kwargs = super().get_form_kwargs()
        kwargs['is_add'] = True 
        kwargs['site_id'] = self.site_id
        return kwargs

    def form_valid(self, form):
        self.object = form.save(commit=False)
        print(vars(self.object))
        dcs_id = self.device_circuit_subnet
        print('ID: {}'.format(dcs_id))
        self.object.save()

控制台输出窗体打印对象

{'_state': <django.db.models.base.ModelState object at 0x7f31fedefcf8>, 'id': None, 'device_id': None, 'circuit_id': None, 'subnet_id': None, 'active_link': False, 'active_link_timestamp': None, 'monitored': False, 'interface_name': 'll', 'get_bgp': False, 'wb_bgp': False, 'db_bgp': False, 'get_interface': False, 'wb_interface': False, 'db_interface': False, 'get_aws': False, 'wb_aws': False, 'db_aws': False}