How to match field of different table in Django - django

Question

I'm using Django as backend, PostgresSQL as DB, and HTML, CSS, and Javascript as frontend. I got stuck to match the field and retrieve specific data in Django.
class Motor(models.Model):
.
.
code = models.CharField(max_length=100)
.
.
class Drum(models.Model):
.
.
code = models.CharField(max_length=100)
.
.
class Cart(models.Model):
.
.
motor = models.ForeignKey(Motor, on_delete=models.CASCADE,null=True, blank=True)
drum = models.ForeignKey(Drum, on_delete=models.CASCADE,null=True, blank=True)
.
.
Now in the Above model, there is the cart Model which saves the data of the Motor Model or else saves the data of the Drum Model or both.
So for example If the user saves the data of the Motor Model in the Cart Model. The data which is saved in the Cart model should match the code field with model Drum and should filter the data accordingly.
So, I have done something like this.
views.py
def Drum(request):
drum_filter = Drum.objects.filter(code__in=Cart.objects.all().values_list('code', flat = True))
return render(request, 'list/drum.html',
{'drum_filter':drum_filter}
)
But now the problem is: The code field in Cart goes as child table and my parent table is Motor. something like this:
[
{
"id": 4,
"quantity": 1,
"user": {
"id": 4,
},
"motor": {
"id": 9,
"name": "...",
"title": "....",
.
.
.
"code": "DD1"
},
"drum": null
}
]
]
Now I unable to match the table field in Django.
So lastly, the code field in the Cart model should match with the code field in the Drum model and if the user does not save any records in the Cart model, then whole Drum model records should filter. Just like this:
Drum = Drum.objects.all().order_by('price')
Last but not least. Is it the right approach to this to filter specific data?

Answer 1

For the first part you could filter as follows
def Drum(request):
drum_filter = Drum.objects.filter(code__in=Cart.objects.values_list('motor__code', flat = True))
return render(request, 'list/drum.html',
{'drum_filter':drum_filter}
)
Second, you can check if cart list is empty
def Drum(request):
carts = Cart.objects.values_list('motor__code', flat = True)
drum_filter = Drum.objects.filter(code__in=carts) if carts else Drum.objects.all().order_by('price')
return render(request, 'list/drum.html',
{'drum_filter':drum_filter}
)
Hope this solves your issue