从已验证的formset中的表单清空cleaning_data（不缺少） - 为什么？

Question

我正在迭代一个formset来处理每个表单，但无论出于何种原因，formset中的表单都有一个空的cleaning_data。

这是我的视图代码（片段）：

 for dform in directors_formset:
                        dform.is_valid() # has no effect on cleaned_data, returns true
                        ddata = dform.cleaned_data
                        email = ddata['officer_email']

Directors_formset已通过验证。 POST请求包含director_formset表单中的字段。但是，ddata == {}。为什么？

编辑：这是表单定义：

class OfficerForm(forms.Form):
        is_secretary = forms.ChoiceField(choices=(('DIR', 'a director'), ('SEC', 'a secretary')),
                                         label='This officer will be:',
                                         initial='DIR',
                                         widget=forms.RadioSelect(renderer=SaneRadioField))
        is_corporate = forms.ChoiceField(initial='IND',
                                         label='This officer is:',
                                         choices=(("IND", "an individual"),
                                                  ("EEA", "incorporated in the EEA (including the UK)"),
                                                  ("FOR", "incorporated outside the EEA")),
                                         widget=forms.RadioSelect(renderer=SaneRadioField))
        given_name = forms.CharField()
        surname = forms.CharField()
        previous_names = forms.CharField()
        residential_address = forms.CharField(widget=forms.Textarea)

        company_name = forms.CharField()
        service_address = forms.CharField(widget=forms.Textarea)
        officer_email = forms.CharField()

        dob = forms.DateField(label='Date of birth:')
        business_occupation = forms.CharField()
        nationality = forms.CharField()
        country_of_residence = forms.CharField()


        where_registered = forms.CharField()
        registration_number = forms.CharField()
        legal_form = forms.CharField()
        governing_law = forms.CharField()