Django: Limiting the number of relationships in a OnetoMany relationship

Question

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>

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

with any additional creating a python error?

Answer 1

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.

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)

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