引用外键中指定的模型中的字段

Question

Say I have a car model that looks like this:

class Car(models.Model):
     car_model = models.CharField(max_length=100)
     car_number = models.IntegerField()

and I also have a wheel model that now looks like this:

class Wheel(models.Model):
    car = models.ForeignKey(Car, on_delete=models.CASCADE)

I want to specify a wheel's model so it has to be the same like its car's model.

something like that:

class Wheel(models.Model):
    car = models.ForeignKey(Car, on_delete=models.CASCADE)
    wheel_model = car.car_model

How can I achieve this? So If my car_model is BMW, I want also to have wheel_model BMW set automatically

Answer 1

You can define a property wheel_model on Wheel .

class Wheel(models.Model):
    car = models.ForeignKey(Car, on_delete=models.CASCADE)

    @property
    def wheel_model(self):
        return self.car.car_model

Now you can access it

wheel_obj.wheel_model