django - 尝试更新模型对象时，类型 'NoneType' 的参数不可迭代

Question

出现错误 Argument of type 'NoneType' is not iterable 并且无法找出原因。

它发生在行 if model_form.is_valid():

View .py

def update_model(request, pricemodel_id):
    """ Update a part given its id. """
    pricemod = Part.objects.get(id=pricemodel_id)
    if request.method == "POST":
        print "post request"
        model_form = priceform(request.POST, request.FILES, instance=pricemod)
        model_form.is_update = True
        if request.user == pricemod.adder:
            #from ipdb import set_trace; set_trace()
            if model_form.is_valid():

表格.py

class priceform(ModelForm):
# price Form: form associated to the Part model
    def __init__(self, *args, **kwargs):
        super(priceform, self).__init__(*args,**kwargs)
        self.is_update=False
        choices = UniPart.objects.all().values('manufacturer').distinct()
    def clean(self):
        if self.cleaned_data and 'modelname' not in self.cleaned_data:
            raise forms.ValidationError("Some error message")
            if not self.is_update:
                return self.cleaned_data
            return self.cleaned_data
    class Meta:
        model = Part

Answer 1

看起来是因为您的 clean 方法中的缩进错误。目前它不返回任何东西，即它返回 None，但必须返回 self.cleaned_data。您所有的 clean 方法代码都在 if 下，这将引发异常。如果此 if 不匹配，则返回 None。

试试这个:

class priceform(ModelForm):
    # ...
    def clean(self):
        if self.cleaned_data and 'modelname' not in self.cleaned_data:
            raise forms.ValidationError("Some error message")
        if not self.is_update:
            return self.cleaned_data
        return self.cleaned_data

    # ...