用类扩展Django ModelForm

Question

我在我的Django项目中有多个模型表单，并且想要为它们添加三个字段。

但是，当我写一个简单的表单，然后子类化它，我得到一个错误。

class PersonForm(forms.Form): 
    person_name = forms.CharField(
     label=u'Entregado por', 
     max_length=64, 
    ) 
    person_document_number = forms.CharField(
     label=u'Número de Documento', 
     max_length=15, 
    ) 
    person_document_type = forms.ChoiceField(
     label=u'Tipo de Documento', 
     choices=BLANK_CHOICE_DASH + list(DOCUMENT_TYPE_CHOICES), 
    ) 

class ContractForm(PersonForm, forms.ModelForm): 
    class Meta: 
     model = Contract 

    def __init__(self, *args, **kwargs): 
     super(ContractForm, self).__init__(*args, **kwargs) 
     self.fields['person_name'].widget.attrs['class'] = 'js-person-name' 

错误：

TypeError: Error when calling the metaclass bases 
    metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases 

我试图定义一个PersonForm像

class PersonForm: 
    person_name = forms.CharField(
     label=u'Entregado por', 
     max_length=64, 
    ) 
    # .... 

未经forms.Form继承它，并得到了一个错误：

django.core.exceptions.FieldError: Unknown field(s) (person_document_type, person_document_number, person_name) specified for Contract 

有没有美丽的方式来做到这一点（没有将这些字段复制到我的模型表单中）？

Answer 1

为什么不直接在ModelForm中实现PersonForm？

class PersonForm(forms.ModelForm): 
    person_name = forms.CharField(
     label=u'Entregado por', 
     max_length=64, 
    ) 
    person_document_number = forms.CharField(
     label=u'Número de Documento', 
     max_length=15, 
    ) 
    person_document_type = forms.ChoiceField(
     label=u'Tipo de Documento', 
     choices=BLANK_CHOICE_DASH + list(DOCUMENT_TYPE_CHOICES), 
    ) 

class ContractForm(PersonForm): 
    class Meta: 
     model = Contract 

    def __init__(self, *args, **kwargs): 
     super(ContractForm, self).__init__(*args, **kwargs) 
     self.fields['person_name'].widget.attrs['class'] = 'js-person-name'