如何在外键 Django 中获取计数项目？

Question

I have two classes of models and I need to get the number of products from a single vendor

class Vendor(models.Model):
    name = models.CharField(max_length=50, unique=True)
    seo_name = models.SlugField()
    product_count = models.IntegerField(default=0)    


class Product(models.Model):
        vendor = models.ForeignKey(Vendor, unique=False, blank=True, default=None, null=True, on_delete=models.SET_NULL)

How to calculate the count of products in the Vendor ?

Answer 1

Take a look on Django recipe: Add an auto-count field to your model tutorial. It totally covers your question.

Good Luck !