django - 限制外键数量

Question

让我们以这个例子为例:

class Team (models.Model):
    name = models.CharField('Name', max_length=30)

class Round (models.Model):
    round_number = models.IntegerField('Round', editable=False) #Auto-incrementing per Team
    team = models.ForeignKey(Team)

有3轮的限制。我如何在管理员内部提出错误并通常阻止团队超过 3 轮？

Answer 1

我喜欢使用验证器的方式:

def restrict_amount(value):
    if Round.objects.filter(team_id=value).count() >= 3:
        raise ValidationError('Team already has maximal amount of rounds (3)')


class Team (models.Model):
    name = models.CharField('Name', max_length=30)


class Round (models.Model):
    round_number = models.IntegerField('Round', editable=False) #Auto-incrementing per Team
    team = models.ForeignKey(Team, validators=(restrict_amount, ))

使用验证器将使 Django 正确处理它，例如，在管理面板中显示错误。