验证管理站点保存在Django中

Question

I have the following two classes defined in models.py

class Part(models.Model):
    name = models.CharField(max_length=32)
    value = models.CharField(max_length=32)

class Car(models.Model):
    name = models.CharField(max_length=32)
    parts = models.ManyToManyField(Part)

So my model allows for multiple parts, but I want the part names to be unique. For example, only one part with name "engine" should be allowed for a given car. How do I enforce this uniqueness?

Things I have looked into:

class save() 

Overriding the default save() for Car doesn't help because parts isn't updated until save is hit.

class save_model()

This will not work because it always saves.

So what are my options for enforcing uniqueness of part names?

UPDATED:

Although I want only one part with name engine to be associated with a car, I still want the ability to define multiple parts with name engine, of course with different values.

So a car with can have a part (part.name=Engine and part.value=V6) and another car can have a part (part.name=Engine and part.value=V4, but a car can't have two parts that have part.name == engine.

Answer 1

EDIT:

class Part(models.Model):
    name = models.CharField(max_length=32)
    value = models.CharField(max_length=32)

class CarPart(models.Model):
    car = models.ForeignKey(Car)
    part_type = models.CharField(max_length=32, unique=true)
    part = models.ForeignKey(Part)

class Car(models.Model):
    name = models.CharField(max_length=32)

treat part_type as part type id (eg type='engine') for engines it will be unique

more about ForeignKey