我遇到了链式下拉菜单的关键错误，逻辑可用于第二个下拉菜单，

问题描述

class PersonCreationForm(forms.ModelForm):
    class Meta:
        model = Person
        fields = '__all__'

    def __init__(self,*args,**kwargs):
        super().__init__(*args,**kwargs)
        self.fields['city'].queryset = City.objects.none()
        # self.fields['city'].queryset = City.objects.all()

        if 'country' in self.data:
            try:
                country_id = int(self.data.get('country'))
                self.fields['city'].queryset = City.objects.filter(country_id=country_id).order_by('name')
            except (ValueError,TypeError):
                pass  # invalid input from the client; ignore and fallback to empty City queryset
        elif self.instance.pk:
            self.fields['city'].queryset = self.instance.country.city_set.order_by('name')

    def __init__(self,**kwargs)
        self.fields['Linename'].queryset=Linename.objects.none()
        # self.fields['city'].queryset = City.objects.all()

        if 'city' in self.data:
            try:
                city_id = int(self.data.get('city'))
                self.fields['Linename'].queryset = Linename.objects.filter(city_id=city_id).order_by('name')
            except (ValueError,TypeError):
                pass  # invalid input from the client; ignore and fallback to empty City queryset
        elif self.instance.pk:
            self.fields['Linename'].queryset = self.instance.city.linename_set.order_by('name')


    def __init__(self,**kwargs)
        self.fields['Instru'].queryset=Instru.objects.none()
        # self.fields['instru'].queryset = Instru.objects.all()

        if 'linename' in self.data:
            try:
                linename_id = int(self.data.get('linename'))
                self.fields['instru'].queryset = Instru.objects.filter(linename_id=linename_id).order_by('name')
            except (ValueError,TypeError):
                pass  # invalid input from the client; ignore and fallback to empty City queryset
        elif self.instance.pk:
            self.fields['instru'].queryset = self.instance.city.Instru_set.order_by('name')

我收到关键错误

self.fields['Instru'].queryset=Instru.objects.none()

非常感谢

解决方法

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