Django：在模型级别而不是列级别应用验证器

Question

假设我有以下 Django 模型：

class PersonClub(models.Model):
    person = models.ForeignKey(Person, on_delete=models.CASCADE)
    club = models.ForeignKey(Club, on_delete=models.CASCADE)
    year = models.PositiveSmallIntegerField()

    class Meta:
        unique_together = ("person", "club", "year")

我需要在模型级别应用一个验证器来执行此规则：

一个人在某一年只能属于 3 个不同的俱乐部。

最好的方法是什么？我想我的验证器应该看起来像这样，但我不知道把它放在哪里：

from django.core.exceptions import ValidationError
from django.utils.translation import gettext_lazy as _

def validate_annual_clubs_per_person(obj):
    count = PersonClub.objects.filter(person=obj.person, year=obj.year).count()
    if count >= 3:
        raise ValidationError(
            _("%(person)s has exceeded max clubs for %(year)s"),
            params={"person": obj.person, "year": obj.year},
        )

Answer 1

# You can put validation in models.py and apply validation for a field

from django.core.exceptions import ValidationError
from django.utils.translation import gettext_lazy as _

def validate_annual_clubs_per_person(obj):
    count = PersonClub.objects.filter(person=obj.person, year=obj.year).count()
    if count >= 3:
        raise ValidationError(
            _("%(person)s has exceeded max clubs for %(year)s"),
            params={"person": obj.person, "year": obj.year},
        )


class PersonClub(models.Model):
    person = models.ForeignKey(Person, on_delete=models.CASCADE, validators=[validate_annual_clubs_per_person])
    club = models.ForeignKey(Club, on_delete=models.CASCADE)
    year = models.PositiveSmallIntegerField()

    class Meta:
        unique_together = ("person", "club", "year")