Auto update model value based on another value in this model django

I have a model called Products. This model has values like this

class Product(models.Model):
    title       = models.CharField(max_length=70, null=True, blank=True)
    producent   = models.CharField(max_length=40, null=True, blank=True)
    stock       = models.PositiveIntegerField(default=0, null=True, blank=True)
    display     = models.BooleanField(null=True, blank=True, default=True)

How can I change display to be False if stock is equal to 0 automatically, so when client buys last product in store display value will change from True to False and

Product.objects.filter(display=True)

will result in products that I want to show or are in stock.

I know that I can simply chain .filter() but I wonder if I can do in an elegant way

Answer

For what you said I think you have a view to decrease stock value

Add this logic to your view, after update the stock value:

if product.stock==0:
    product.display = False
    product.save()

Considering that your view (used to decrease stock value) already instantiated the target “product”. If that don’t help you, please, post your view.py, to give us more information.