python - Django max_length 另一个模型属性

Question

我希望一个模型属性的整数值是另一个模型属性的 max_length，如下所述“capacity = models.IntegerField(ma​​x_length=Concerthall.capacity)”。

class Concerthall(models.Model):
    name = models.TextField(max_length=254)
    capacity = models.IntegerField()
    employees = models.IntegerField()

    def __str__(self):
    return self.name

class Events(models.Model):
    name = models.TextField(max_length=254)
    capacity = models.IntegerField(max_length=Concethall.capacity)
    timeFrom = models.DateTimeField()
    timeTo = models.DateTimeField()
    concerthallName = models.ForeignKey(Concerthall, on_delete=models.PROTECT, null=True)

也许它也与验证器一起工作，但我搜索了几个小时，但无法找到任何解决方案。

Answer 1

我建议采用不同的方法，在模型中进行验证 clean()方法:

class Events(models.Model):
    name = models.TextField(max_length=254)
    capacity = models.IntegerField(default=0)
    timeFrom = models.DateTimeField()
    timeTo = models.DateTimeField()
    concert_hall = models.ForeignKey(Concerthall, on_delete=models.PROTECT)

    def clean(self):
        if self.capacity > self.concert_hall.capacity:
            raise ValidationError(
                'the capacity of the event cannot exceed the capacity of the hall')