Django：限制OnetoMany关系中的关系数量 [英] Django: Limiting the number of relationships in a OnetoMany relationship

问题描述

你好，我希望将ForeignKey关系限制为具体数字。

让我们说篮球队只能有12个人。

Hi i was looking to limit a ForeignKey relationship to as specific number.
Lets say there can only be 12 people on a basketball team.

class Team(models.Model):
 teamName = models.CharField(max_length = 20)
 teamColors = models.CharField(max_length = 20)
 ... <and so forth>

class Player(models.Models):
 team = models.ForeignKey(Team, **)
 name = models.CharField(max_length = 20)
 heightInches = models.IntegerField()
 ... <and so forth>

**是否有一个选项可以限制每个团队12位玩家？

** is there an option to would limit up to 12 players per team here?

与任何额外的创建一个python错误？

with any additional creating a python error?

推荐答案

没有直接方式来限制一个团队中的ForeignKey定义的玩家人数。然而，这可以通过一些使用你的模型来完成。

There isn't a direct way to limit the number of players in a team on the ForeignKey definition. However, this can be done with a little bit of working with your model.

一个选项是在Team上创建一个方法，如：

One option would be to make a method on Team, something like:

def add_player(self, player):
    if self.player_set.count() >= 12:
         raise Exception("Too many players on this team")

    self.player_set.add(player)

然后，您可以随时通过此方法添加玩家。

Then you would want to always add players through this method.

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