在childs对象中设置父对象值'；是Django的模型形式吗？

我希望在孩子的模型中预先填充一个家长变量，特别是序列号。我已经设法将序列号作为URL的一部分，但我想知道如何将其作为表单页面上的变量实现

型号.py

class Product(models.Model):
  serial_number = models.CharField(unique=True, max_length=15)

class ProductInstance(models.Model):
  serial_number = models.ForeignKey('Product', on_delete=models.SET_NULL, null=True)

class ProductInstanceCreate(CreateView):
  model = ProductInstance
  template_name = 'myapp/edit_productinstance.html'
  form_class = GunInstanceForm

def get_success_url(self):
   return reverse_lazy ('product-detail', kwargs={'pk': self.object.serial_number.pk})

class ProductInstanceForm(forms.ModelForm):

class Meta:
    model = ProductInstance
    fields = '__all__'

urlpatterns += [  
url(r'^productinstance/(?P<serial_number>[-\w]+)/create/$', views.ProductInstanceCreate.as_view(), name='productinstance_create'),]

视图.py

class Product(models.Model):
  serial_number = models.CharField(unique=True, max_length=15)

class ProductInstance(models.Model):
  serial_number = models.ForeignKey('Product', on_delete=models.SET_NULL, null=True)

class ProductInstanceCreate(CreateView):
  model = ProductInstance
  template_name = 'myapp/edit_productinstance.html'
  form_class = GunInstanceForm

def get_success_url(self):
   return reverse_lazy ('product-detail', kwargs={'pk': self.object.serial_number.pk})

class ProductInstanceForm(forms.ModelForm):

class Meta:
    model = ProductInstance
    fields = '__all__'

urlpatterns += [  
url(r'^productinstance/(?P<serial_number>[-\w]+)/create/$', views.ProductInstanceCreate.as_view(), name='productinstance_create'),]

Forms.py

class Product(models.Model):
  serial_number = models.CharField(unique=True, max_length=15)

class ProductInstance(models.Model):
  serial_number = models.ForeignKey('Product', on_delete=models.SET_NULL, null=True)

class ProductInstanceCreate(CreateView):
  model = ProductInstance
  template_name = 'myapp/edit_productinstance.html'
  form_class = GunInstanceForm

def get_success_url(self):
   return reverse_lazy ('product-detail', kwargs={'pk': self.object.serial_number.pk})

class ProductInstanceForm(forms.ModelForm):

class Meta:
    model = ProductInstance
    fields = '__all__'

urlpatterns += [  
url(r'^productinstance/(?P<serial_number>[-\w]+)/create/$', views.ProductInstanceCreate.as_view(), name='productinstance_create'),]

模板/myapp/product\u detail.html

...
<a href="{% url 'productinstance_create' serial_number=product.serial_number %}">New</a>
...

{% extends "base_generic.html" %}
{% block content %}


<h2>Serial Number: {{ serial_number }}</h2>
</br>
<form action="" method="post">

    {% csrf_token %}
    <table>
    {{ form }}
    </table>
    <input type="submit" value="Submit" />
</form>
</br>
<a href="">Back</a>

{% endblock %} 

。。。
...

url.py

class Product(models.Model):
  serial_number = models.CharField(unique=True, max_length=15)

class ProductInstance(models.Model):
  serial_number = models.ForeignKey('Product', on_delete=models.SET_NULL, null=True)

class ProductInstanceCreate(CreateView):
  model = ProductInstance
  template_name = 'myapp/edit_productinstance.html'
  form_class = GunInstanceForm

def get_success_url(self):
   return reverse_lazy ('product-detail', kwargs={'pk': self.object.serial_number.pk})

class ProductInstanceForm(forms.ModelForm):

class Meta:
    model = ProductInstance
    fields = '__all__'

urlpatterns += [  
url(r'^productinstance/(?P<serial_number>[-\w]+)/create/$', views.ProductInstanceCreate.as_view(), name='productinstance_create'),]

urlpatterns+=[
url（r'^productinstance/（？P[-\w]+）/create/$，views.ProductInstanceCreate.as_view（），name='productinstance_create'），]

模板/myapp/edit\u productinstance\u form.html

...
<a href="{% url 'productinstance_create' serial_number=product.serial_number %}">New</a>
...

{% extends "base_generic.html" %}
{% block content %}


<h2>Serial Number: {{ serial_number }}</h2>
</br>
<form action="" method="post">

    {% csrf_token %}
    <table>
    {{ form }}
    </table>
    <input type="submit" value="Submit" />
</form>
</br>
<a href="">Back</a>

{% endblock %} 

{%extensed“base_generic.html”%}
{%block content%}
序列号：{{序列号}


{%csrf_令牌%}
{{form}}


{%endblock%}

因此，目前我可以创建一个URL，例如：productinstance/D1430913/create/

我现在需要知道：

如何将其用作标题的变量

如何将表单默认值设置为它

标题：

<h2>Serial Number: {{ form.serial_number.value }}</h2>