保存模型表单给出“NoneType”对象不可迭代错误

Question

我在一个模板中显示一个表单和一个表单集，并尝试保存它们。 Formset 可以很好地保存，但是当我添加表单时，它会给出 'NoneType' object is not iterable 错误。

Django 显示我在这个阶段出错，Chrome 显示我的变量如下。

问题行：po = purchaseorder_form.save()

▼ 局部变量

ProductBatchFormset <"class 'django.forms.formsets.ProductBatchFormFormSet'>

productbatch_formset <"django.forms.formsets.ProductBatchFormFormSet object at 0x10bc39950">

purchaseorder_form <"PurchaseOrderForm bound=True, valid=True, fields=(purchaseOrderId;issuedBy;issuedAt;issuedTo;referencePurchaseOrders;internalManager;note;productSpendType)">

request <"WSGIRequest: POST '/purchaseorder/create?submitted=True'">

submitted False

完整追溯

Traceback (most recent call last):
  File "/Users/marinalee/.local/share/virtualenvs/scm-SrDaDYy6/lib/python3.7/site-packages/django/core/handlers/exception.py", line 34, in inner
    response = get_response(request)
  File "/Users/marinalee/.local/share/virtualenvs/scm-SrDaDYy6/lib/python3.7/site-packages/django/core/handlers/base.py", line 115, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "/Users/marinalee/.local/share/virtualenvs/scm-SrDaDYy6/lib/python3.7/site-packages/django/core/handlers/base.py", line 113, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/Users/marinalee/django-projects/scm/purchaseorders/views.py", line 22, in create_purchaseOrder
    po = purchaseorder_form.save()
  File "/Users/marinalee/.local/share/virtualenvs/scm-SrDaDYy6/lib/python3.7/site-packages/django/forms/models.py", line 459, in save
    self._save_m2m()
  File "/Users/marinalee/.local/share/virtualenvs/scm-SrDaDYy6/lib/python3.7/site-packages/django/forms/models.py", line 441, in _save_m2m
    f.save_form_data(self.instance, cleaned_data[f.name])
  File "/Users/marinalee/.local/share/virtualenvs/scm-SrDaDYy6/lib/python3.7/site-packages/django/db/models/fields/related.py", line 1621, in save_form_data
    getattr(instance, self.attname).set(data)
  File "/Users/marinalee/.local/share/virtualenvs/scm-SrDaDYy6/lib/python3.7/site-packages/django/db/models/fields/related_descriptors.py", line 975, in set
    objs = tuple(objs)
TypeError: 'NoneType' object is not iterable

# forms.py
class PurchaseOrderForm(forms.ModelForm):
    class Meta:
        model = PurchaseOrder
        fields = '__all__'
    issuedAt = forms.DateField(
    widget=forms.DateInput(format='%Y%m%d', attrs={'placeholder': 'YYYYMMDD'}),
    input_formats=('%Y%m%d', )
    )
    referencePurchaseOrders = forms.ModelChoiceField(widget=forms.SelectMultiple, queryset=PurchaseOrder.objects.all(), required=False)
    internalManager = forms.ModelChoiceField(queryset=CustomUser.objects.all(), required=False)
    issuedBy = forms.ModelChoiceField(queryset=Company.objects.all(), required=False)
    issuedTo = forms.ModelChoiceField(queryset=Company.objects.all(), required=False)
    productSpendType = forms.ModelChoiceField(queryset=ProductSpendType.objects.all(), required=False)

class ProductBatchForm(forms.ModelForm):
    class Meta:
        model = ProductBatch
        fields = '__all__'

    product = forms.ModelChoiceField(queryset=Product.objects.all(), required=False)
    quantity = forms.CharField(required=False)
    unitprice = forms.CharField(required=False)
    unitcurrency = forms.ModelChoiceField(queryset=Currency.objects.all(), required=False)
    productSpendType = forms.ModelChoiceField(queryset=ProductSpendType.objects.all(), required=False)

# models.py
class PurchaseOrder(models.Model):
    def __str__(self):
        return str(self.pk)
    purchaseOrderId = models.CharField(max_length=30, null=True, blank=True, db_index=True)
    issuedBy = models.ForeignKey('users.Company', null=True, blank=True, db_index=True, on_delete=models.CASCADE, related_name='issued_POs')
    issuedAt = models.DateTimeField(null=True, blank=True, db_index=True)
    issuedTo = models.ForeignKey('users.Company', null=True, blank=True, db_index=True, on_delete=models.CASCADE, related_name='received_POs')
    referencePurchaseOrders = models.ManyToManyField('self', symmetrical=False, null=True, blank=True, db_index=True, related_name='related_POs')
    internalManager = models.ForeignKey('users.CustomUser', null=True, blank=True, db_index=True, on_delete=models.CASCADE, related_name='managed_POs')
    note = models.TextField(max_length=500, null=True, blank=True, db_index=True)

class ProductBatch(models.Model):
    def __str__(self):
        return str(self.pk)
    purchaseOrder = models.ForeignKey('PurchaseOrder', null=True, blank=True, db_index=True, on_delete=models.CASCADE)
    product = models.ForeignKey('products.Product', null=True, blank=True, db_index=True, on_delete=models.CASCADE)
    quantity = models.IntegerField(null=True, blank=True, db_index=True)
    unitprice = models.DecimalField(max_digits=20, decimal_places=2, null=True, blank=True, db_index=True)
    unitcurrency = models.ForeignKey('payments.Currency', null=True, blank=True, db_index=True, on_delete=models.CASCADE)
    productSpendType = models.ForeignKey('ProductSpendType', on_delete=models.CASCADE, null=True, blank=True, db_index=True)

#views.py
def create_purchaseOrder(request):
    submitted = False
    ProductBatchFormset = formset_factory(ProductBatchForm, extra=1, can_order=True, can_delete=True)

    if request.method == 'POST':
        purchaseorder_form = PurchaseOrderForm(request.POST)
        productbatch_formset = ProductBatchFormset(request.POST, prefix = 'pb')
        if purchaseorder_form.is_valid() and productbatch_formset.is_valid():
            po = purchaseorder_form.save()
            for form in productbatch_formset:
                pb = form.save()
            return HttpResponseRedirect('/purchaseorder/create?submitted=True')
        else:
            return HttpResponseRedirect('/purchaseorder/create?'+str(purchaseorder_form.errors))
    else:
        context = {
            'purchaseorder_form': PurchaseOrderForm(),
            'productbatch_formset': ProductBatchFormset(prefix='pb')
        }
        return render(request, 'createpo.html', context)

#template
  <form action="" method="post" id="myForm">
    {% csrf_token %}
    <div class="form-row" >
      <div class="form-group col-md-3">
        <label for="issuedBy" class="control-label">Issued by</label>
        {{purchaseorder_form.issuedBy}}
      </div>
      <div class="form-group col-md-3">
        <label for="issuedTo" class="control-label">Issued to</label>
        {{purchaseorder_form.issuedTo}}
      </div>             
     </div>
     <div class="form-row"> 
      <div class="form-group col-md-2">
        <label for="purchaseOrderId" class="control-label">PO number</label>
        {{purchaseorder_form.purchaseOrderId}}
      </div>
      <div class="form-group col-md-2">
        <label for="issuedAt" class="control-label">PO date</label>
        {{purchaseorder_form.issuedAt}}
      </div>
    </div>
    <div class="form-row">
      <div class="form-group col-md-4">
        <label for="internalManager" class="control-label">Manager</label>
        {{purchaseorder_form.internalManager}}
      </div>    
    </div>
    <div class="form-row">
      <div class="form-group col-md-4">
        <label for="referencePurchaseOrders" class="control-label">Reference POs</label>
        {{purchaseorder_form.referencePurchaseOrders}}
      </div>         
    </div>
    <div class="form-row">
      <div class="form-group col-md-4">
        <label for="note" class="control-label">Notes</label>
        {{purchaseorder_form.note}}
      </div>   
    </div>
    <br/>

    <table border="0" cellpadding="0" cellspacing="0">
        <tbody>
            {% for productbatch_form in productbatch_formset.forms %}
            <tr>
               <td>Product: {{productbatch_form.product}}</td>
               <td>Quantity: {{productbatch_form.quantity}}</td>
               <td>Currency: {{productbatch_form.unitcurrency}}</td>
               <td>Unit Price: {{productbatch_form.unitprice}}</td>
               <td>Spend Type: {{productbatch_form.productSpendType}}</td>
            </tr> 
            {% endfor %}
        </tbody>
    </table>
    {{ productbatch_formset.management_form }}

  <div>
<br/><br/>
<button class="btn btn-primary" type="submit">Create PO</button></div>
    {% csrf_token %}
  </form>

我希望表单和 formset 中的表单一样保存，但只有 formset 中的表单在保存。非常感谢您的帮助！

Answer 1

问题似乎在于，当没有选择参考采购订单并且内部多对多代码需要可迭代时，referencePurchaseOrders 字段的 SelectMultiple 小部件返回 None。我尚未对此进行测试，但我相信以下方法会起作用：

class PurchaseOrderForm(forms.ModelForm):
    ... # your existing form definition code here
    # add some additional validation to return an empty list
    # if no referencePurchaseOrders are selected
    def clean_referencePurchaseOrders(self):
        pos = self.cleaned_data.get("referencePurchaseOrders")
        if pos is None:
            return []
        return pos