How to filter dropdown choices based on the value of another dropdown in Django Admin? - django-admin

Question

Consider we have the following models:
class Shop(models.Model):
...
class Item(model.Models):
shop = models.ForeignKey('Shop') # Shop where the item is stored.
...
class Order(models.Models):
shop = models.ForeignKey('Shop') # Shop where the ordered item is stored
item = models.ForeignKey('Item') # Ordered item
We are using Django Admin for the creation of orders.
On the "Create Order" page of Django admin, there are 2 dropdowns "Shop" dropdown and "Item" dropdown.
When I choose the shop in the "Shop" dropdown I want the choices in the "Item" dropdown to contain items which are available only in the chosen shop.
How can I implement that?

Answer 1

If you want to filter results based on the value of other fields in form then you can implement this with the help of javascript or Ajax call.
If you don't want write javascript or ajax code then you can use django-autocomplete-light package.
you create a form and forward selected value of shop for item field in the form and access in the view where you can set queryset for item form field. You can also search in item field value.
In forms.py,
from django import forms
from dal import autocomplete
class OrderForm(forms.ModelForm):
item = forms.ModelChoiceField(
queryset=Item.objects.all(),
widget=autocomplete.ModelSelect2(
url='item_autocomplete',
forward=['shop']
),
)
class Meta:
model = Order
fields = "__all__"
In urls.py,
urlpatterns = [
path('item_autocomplete/', ItemAutocompleteView.as_view(), name='item_autocomplete'),
]
In views.py,
from dal import autocomplete
from .models import Item
class ItemAutocompleteView(autocomplete.Select2QuerySetView):
def get_queryset(self):
if not self.request.user.is_authenticated:
return Item.objects.none()
shop = self.forwarded.get('shop', None)
if shop:
qs = Item.objects.filter(shop=shop)
else:
qs = Item.objects.none()
# I assume your Item model has `title` field (this is searchable column. you can search on field value )
if self.q:
qs = qs.filter(title__istartswith=self.q)
return qs
In admin.py,
#admin.register(Order)
class OrderAdmin(admin.ModelAdmin):
form = OrderForm
...
forward value doc link- https://django-autocomplete-light.readthedocs.io/en/master/tutorial.html#filtering-results-based-on-the-value-of-other-fields-in-the-form