Django-ModelForm can_delete = True不适用于M2M（直通）模型 [英] Django - ModelForm can_delete=True not working with M2M (through) model

问题描述

选中删除复选框后，提交表单时不会删除LayerMapOptions实例。否则，该表格对于所有其他字段都可以正常使用。

When the delete checkbox is checked, the LayerMapOptions instance is not deleted when the form is submitted. Otherwise the form is working perfectly for all other fields. Is there something special to do in the form for through model?

model：

class EzMap(models.Model):
    map_name = models.SlugField(max_length=50)
    layers = models.ManyToManyField(Shapefile, through='LayerMapOptions', verbose_name='Layers to display', null=True, blank=True)

class Shapefile(models.Model):
    filename = models.CharField(max_length=255)

class LayerMapOptions(models.Model):
    layer = models.ForeignKey(Shapefile)
    ezmap = models.ForeignKey(EzMap)
    position = models.IntegerField(max_length=100)
    visible = models.BooleanField()

view：

def setMapOptions(request, map_name):
    map_selected = EzMap.objects.get(map_name=map_name, created_by=request.user)
    layers_ordered = LayerMapOptions.objects.filter(ezmap=map_selected).order_by('position')
    layerForm = modelformset_factory(LayerMapOptions, form=LayerMapOptionsForm, extra=0, can_delete=True)
        if request.POST:
            formset = layerForm(request.POST, queryset=layers_ordered)
            pk_list = request.POST.get("layersOrder")

            if formset.is_valid():
                for form in formset:
                    instance = form.instance
                    instance.position = pk_list.index(instance.pk)
                    instance.save()

            save_link = u"/ezmapping/map/%s" % (map_name)
            return HttpResponseRedirect(save_link)
        else:
            formset = layerForm(queryset=layers_ordered)
     return render_to_response("ezmapping/manage_map_Options.html", {'formset': formset}, context_instance=RequestContext(request))

表格：

class LayerMapOptionsForm(ModelForm):
    link = forms.CharField(label='link', required=False)

    def __init__(self, *args, **kwargs):
        super(LayerMapOptionsForm, self).__init__(*args, **kwargs)
        self.fields['link'].widget = ModelLinkWidget(self.instance.layer)

    class Meta:
        model = LayerMapOptions
        fields =  ['link', 'visible']

推荐答案

您正在保存单个实例。相反，您需要在表单集上调用save（）来触发自动删除所选项目。仔细阅读文档。

You are saving single instances. Instead you need to call save() on the formset to trigger automatic removal of selected items. Read docs more carefully.

https://docs.djangoproject.com/en/1.5/topics/forms/formsets/#can-delete

如果使用的是ModelFormSet，则在调用formset.save（）时将删除已删除表单的模型实例。另一方面，如果您使用的是简单的FormSet，则由您决定是否要处理formset.deleted_forms，可能是在您的setset的save（）方法中，因为对于删除表单的含义并没有普遍的认识。

If you are using a ModelFormSet, model instances for deleted forms will be deleted when you call formset.save(). On the other hand, if you are using a plain FormSet, it’s up to you to handle formset.deleted_forms, perhaps in your formset’s save() method, as there’s no general notion of what it means to delete a form.

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