为什么这些类属性不注册？

Question

我有一个工厂方法，它生成django表单类，如下所示：

def get_indicator_form(indicator, patient):
    class IndicatorForm(forms.Form):
        #These don't work!
        indicator_id = forms.IntegerField(initial=indicator.id, widget=forms.HiddenInput())
        patient_id = forms.IntegerField(initial=patient.id, widget=forms.HiddenInput())

        def __init__(self, *args, **kwargs):
            forms.Form.__init__(self, *args, **kwargs)
            self.indicator = indicator
            self.patient = patient

    #These do!
    setattr(IndicatorForm, 'indicator_id',  forms.IntegerField(initial=indicator.id, widget=forms.HiddenInput()))
    setattr(IndicatorForm, 'patient_id', forms.IntegerField(initial=patient.id, widget=forms.HiddenInput()))

    for field in indicator.indicatorfield_set.all():
        setattr(IndicatorForm, field.name, copy(field.get_field_type()))

    return type('IndicatorForm', (forms.Form,), dict(IndicatorForm.__dict__))

我试图理解为什么顶级表单字段声明不起作用，但是下面的setattr方法确实起作用。我对python相当陌生，所以我怀疑这是我误解的语言特性。你能帮助我理解为什么类顶部的字段声明没有将字段添加到类中吗？你知道吗

在一个可能相关的注释中，当实例化这些类时，instance.media将不返回任何内容，即使某些字段具有与媒体相关联的小部件。你知道吗

谢谢你， 皮特

Answer 1

试试这个：

def get_indicator_form(indicator, patient):
    class IndicatorForm(forms.Form):
        indicator_id = forms.IntegerField(initial=indicator.id, widget=forms.HiddenInput())
        patient_id = forms.IntegerField(initial=patient.id, widget=forms.HiddenInput())

        def __init__(self, *args, **kwargs):
            forms.Form.__init__(self, *args, **kwargs)
            self.indicator = indicator
            self.patient = patient

    for field in indicator.indicatorfield_set.all():
        IndicatorForm.base_fields[field.name] = field.get_field_type()

    return IndicatorForm