如何在Django表单中传递self.请求数据

我想在Form类中传递self.request个数据.我可以在视图中访问它，但不能在Form类中访问它.

class AttendanceCreateView(LoginRequiredMixin, CreateView):
    model = Attendance
    template_name = 'attendance/attendances_new.html'
    form_class = AttendanceForm

    def get_initial(self):
        initial = super().get_initial()
        initial['class_name'] = self.request.GET.get('class', '')
        return initial

我的表单类:

class AttendanceForm(forms.ModelForm):
    class_name = forms.ChoiceField(choices=CLASS_NAMES, disabled=True)
    teacher = forms.ModelMultipleChoiceField(
        queryset=Teacher.objects.all().order_by('id'))
    subject_name = forms.ChoiceField(choices=[])
    total_students = forms.IntegerField(initial=0)
    unique_code = forms.IntegerField(initial=0)

    class Meta:
        model = Attendance
        fields = ['class_name', 'teacher', 'subject_name',
                  'total_students', 'unique_code']

    def __init__(self, *args, **kwargs):
        super(AttendanceForm, self).__init__(*args, **kwargs)
        
        # This I need to be done
        # if self.request.GET.get('class', '') = 'class1':
        #    self.fields['subject_name'].choices = MY_CHOICES_1 
        # elif self.request.GET.get('class', '') = 'class2':
        #    self.fields['subject_name'].choices = MY_CHOICES_2
        

我想根据传递的请求值设置subject_name个选项.对于第一类，我想要不同的主题 Select .对于第二类，我想要不同的主题 Select 等等.因此，获取请求数据是很重要的.

有没有办法在直接视图中设置初始选项，就像我在class_name中所做的那样？或者对如何在形式上做到这一点有什么建议？