Django formset with manytomany through intermediate model

我想將數據保存到中間模型並在模型中進行一些計算（通過重寫模型保存）。我遇到的問題是formset無法保存到中間模型。Django formset with manytomany through intermediate model

中介模型僅在存在M2M關係時創建（據我瞭解）。

我有4種型號，像這樣：

Category(models.Model): 
    name = models.CharField(..) 

Tax(models.Model): 
    name = models.CharField(..) 
    rate = models.DecimalField(..) 

CategoryItem(models.Model): 
    category = models.ForeignKey(Category) 
    taxes = models.ManyToManyField(Tax, through='CategoryItemTax', through_fields=('item', 'tax')) 
    quantity = models.DecimalField(..) 
    price = models.DecimalField(..) 

# intermediary model below 
CategoryItemTax(models.Model): 
    category = models.ForeignKey(Category) 
    tax = models.ForeignKey(Tax) 
    item = models.ForeignKey(CategoryItem) 
    rate = models.DecimalField(..) #derived from tax object in the model 
    total_tax = models.DecimalField(..) #calculated in model save

我我有CategoryItem表單集一類模型的形式。我的views.py如下：

class FormsetMixin(object): 
    object = None 

    def post(self, request, *args, **kwargs): 
     if getattr(self, 'is_update_view', False): 
      self.object = self.get_object() 
     form_class = self.get_form_class() 
     form = self.get_form(form_class) 
     formset_class = self.get_formset_class() 
     formset = self.get_formset(formset_class) 
     if form.is_valid() and formset.is_valid(): 
      return self.form_valid(form, formset) 
     else: 
      return self.form_invalid(form, formset) 

    # THE SAVE METHOD 
    def form_valid(self, form, formset): 
     self.object = form.save() 
     formset.instance = self.object 
     instances = formset.save(commit=False) 
     for i in instances: 
      CategoryItemTax.objects.create(category=self.object, item=i, tax=i) 
      CategoryItemTax.save() 

class CategoryCreateView(FormsetMixin, CreateView): 
    template_name='..' 
    model = Category 
    form_class = CategoryForm 
    formset_class = CategoryItemFormSet

Forms.py如下

class CategoryForm(forms.ModelForm): 

    class Meta: 
     model = Category 

class CategoryItemForm(forms.ModelForm) 
    class Meta: 
     model = CategoryItem 

CategoryItemFormSet = inlineformset_factory(Category, CategoryItem, form=CategoryItemForm, extra=1)

不幸的是，我得到下面的錯誤：

Cannot set values on a ManyToManyField which specifies an intermediary model. 
Use category.CategoryItemTax's Manager instead

來源

2017-06-03 Hdman

你可以顯示錶單嗎？ – zaidfazil

我已經添加了forms.py代碼。 – Hdman

編輯您的看法是這樣，

def form_valid(self, form, formset): 
    self.object = form.save() 
    formset.instance = self.object 
    instances = formset.save(commit=False) 
    for each in instances: 
     each.category = self.object 
     each.save() 
     item = CategoryItemTax.objects.create(category=self.object, item=each) 
     item.save()

多對多相關對象mus先保存以便與另一個實例關聯。

來源

2017-06-04 17:16:59 zaidfazil

'不能在指定中介模型的ManyToManyField上設置值。改爲使用category.CategoryItemTax的經理。「 - 這是不斷出現的錯誤。 – Hdman

您需要明白，在此視圖中沒有創建Tax對象。爲了創建多對多關係，需要Tax對象以及CategoryItem對象。如果您想在此解釋您要完成的任務，或許我可以提供更多幫助 – zaidfazil

這是一個簡單的開票申請，您可以爲每個分類項目（訂單項）添加多個稅款。 – Hdman

Django formset with manytomany through intermediate model

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