在Django CreateView中保存反向外键

from django.db import models

class A(models.Model):
    name = models.CharField(max_length=100)

class B(models.Model):
    a = models.ForeignKey(A, on_delete=models.CASCADE, related_name='b_objects')
    name = models.CharField(max_length=100)

from django.views.generic.edit import CreateView
from .models import A, B
from .forms import BForm

class BCreateView(CreateView):
    model = B
    form_class = BForm
    template_name = 'b_create.html'

from django import forms
from .models import B

class BForm(forms.ModelForm):
    class Meta:
        model = B
        fields = ['a', 'name']

<form method="post">
  {% csrf_token %}
  {{ form.as_p }}
  <button type="submit">保存</button>
</form>

from django.urls import path
from .views import BCreateView

urlpatterns = [
    path('b/create/', BCreateView.as_view(), name='b_create'),
]