Django - Display child elements based on parent in ModelChoiceField queryset - django

Question

I have created models that each of them based on own parent. On forms I have used ModelChoiceField. When the user selects the element from Category choice field, on Subcategory field should be displayed only its child elements. And also after selecting the Subcategory, on ProductCategory choice field should be displayed child elements.
it should have been something like this
But I am getting error:
TypeError: Field 'id' expected a number but got <django.forms.models.ModelChoiceField object at 0x7f3d1f9f0ac0>. How can I improve it?
models.py:
class Category(models.Model):
name = models.CharField("Category Name", max_length=100, unique=True)
link = models.CharField("Category Link", max_length=250)
def __str__(self):
return self.name
class Subcategory(models.Model):
parent = models.ForeignKey(Category, on_delete=models.CASCADE, null=True)
name = models.CharField("Sub-category Name", max_length=100, unique=True)
link = models.CharField("Sub-category Link", max_length=250)
def __str__(self):
return self.name
class ProductCategory(models.Model):
parent = models.ForeignKey(Subcategory, on_delete=models.CASCADE, null=True)
name = models.CharField("Product-Category Name", max_length=100, unique=True)
link = models.CharField("Product-Category Link", max_length=250)
def __str__(self):
return self.name
class ProductSubCategory(models.Model):
parent = models.ForeignKey(ProductCategory, on_delete=models.CASCADE, null=True)
name = models.CharField("Product-Sub-Category Name", max_length=100, unique=True)
link = models.CharField("Product-Sub-Category Name", max_length=250)
def __str__(self):
return self.name
forms.py
class CategoryForm(forms.Form):
category = forms.ModelChoiceField(queryset=Category.objects.all())
subcategory = forms.ModelChoiceField(queryset=Subcategory.objects.filter(parent=category))
prodcategory = forms.ModelChoiceField(queryset=ProductCategory.objects.filter(parent=subcategory))
On views.py I am just running external script
def homepage(request):
context = {}
form = CategoryForm()
context['form'] = form
if request.GET:
temp = request.GET['prodcategory']
selected = ProductCategory.objects.get(pk=temp)
scraper = Scraper()
results = scraper.scrape(title=selected, link=selected.link)
data = ProductSubCategory.objects.filter(parent=results)
context['data'] = data
return render(request, 'index.html', context)

Answer 1

There is a well explained article on how to approach chained drop down lists in Django forms :
How to Implement Dependent/Chained Dropdown List with Django
or you could use an external library like django-smart-selects