How can I create categories and subcategories in django models?

March 3, 2024

I am building a simple website for a car marketplace. I have written the brand, series and car models. (I purposefully want to treat each of them as seperate models.) Whenever I create a car in the admin panel I want to be able to pick a car brand – let’s say Mercedes – and when I choose the brand I want the next option to be only the series of Mercedes not the series of other cars.

Here is a representation of my code so far:

class Brand(models.Model):
    brand = models.CharField(max_length=100)

class Series(models.Model):
    brand = models.ForeignKey(Brand, on_delete=models.CASCADE)
    series = models.CharField(max_length=100)

class Car(models.Model):
    brand = models.ForeignKey(Brand, on_delete=models.CASCADE)
    series = models.ForeignKey(Series, on_delete=models.CASCADE)

>Solution :

Use a ChainedForeignKey ^{[readthedocs.io]} instead from the django-smart-selects package ^{[readthedocs.io]}:

from smart_selects.db_fields import ChainedForeignKey


class Car(models.Model):
    brand = models.ForeignKey(Brand, on_delete=models.CASCADE)
    series = ChainedForeignKey(
        Series,
        chained_field='brand',
        chained_model_field='brand',
        show_all=False,
        on_delete=models.CASCADE,
    )