Django - 如何创建依赖选择

Question

My task is to implement a form in which the choice of the value of the second field depends on the value of the first field. (For example, if the value of the first field is Cars, then the second field should show sedan/SUV, etc., if the value of the first field is Commercial vehicles, then the second box should show truck/bus, etc.)

Code models.py :

class TypeTransport(models.Model):
    transport_name = models.CharField(max_length=100, verbose_name='kind of transport')


class TypeBodyTransport(models.Model):
    transport = models.ForeignKey(TypeTransport, on_delete=models.CASCADE, blank=True, null=True,
                                  verbose_name='kind of transport')
    body_name = models.CharField(max_length=100, verbose_name='transport body type')


class Advertisement(models.Model):
    transport = models.ForeignKey(TypeTransport, on_delete=models.SET_NULL, blank=True, null=True,
                                  verbose_name='kind of transport')
    body = models.ForeignKey(TypeBodyTransport, on_delete=models.SET_NULL, blank=True, null=True,
                             verbose_name='transport body type ')

Code forms.py :

class CreateAdvertisementForm(forms.ModelForm): 
    transport = forms.ModelChoiceField(queryset=TypeTransport.objects.all(), to_field_name="transport_name")
    body = forms.ModelChoiceField(queryset=TypeBodyTransport.objects.filter(transport=transport),
                                  to_field_name="body_name")
    class Meta:
        model = Advertisement
        fields = ('transport', 'body')

I thought it could be done with filter(transport=transport) , but this error is returned: TypeError: Field 'id' expected a number but got <django.forms.models.ModelChoiceField object at 0x7f40d7af5ac0>.

Can you please tell me how to implement the feature I need?

Answer 1

have you tried:

class CreateAdvertisementForm(forms.ModelForm): 
    transport = forms.ModelChoiceField(queryset=TypeTransport.objects.all(), to_field_name="transport_name")
    body = forms.ModelChoiceField(queryset=TypeBodyTransport.objects.filter(transport=transport.id),
                                  to_field_name="body_name")
    class Meta:
        model = Advertisement
        fields = ('transport', 'body')

instead of transport = transport , try transport = transport.id

Answer 2

I solved this problem using the django-smart-selects library. Additionally I can say that in the forms it is necessary to remove field which references to the ModelChoiceField , because it interferes with its queryset parameter. I'm still a beginner, so I didn't immediately guess that the problem was in chained selects (I edited the question).