Question

I’m starting to work on a small soccer league management website (mostly for learning purposes) and can’t wrap my mind around a Django models relationship. For simplicity, let’s say I have 2 types of objects – Player and Team. Naturally, a player belongs to one team so that’s a ForeignKey(Team) in the Player model.
So I go:

class Team(models.Model):
    name = models.CharField()
class Player(models.Model):
    name = models.CharField()
    team = models.ForeignKey(Team)

Then I want each team to have a captain which would be one of the players so that would be a ForeignKey(Player) in the Team model. But that would create a circular dependency.
Granted my Django experience is limited, but it seems like a simple problem, though I can’t figure out what I’m doing wrong conceptually.

Answer 1

Here is another way to tackle this problem.
Instead of creating a circular dependency, I created an additional table that stores the relationship between players and teams. So in the end it looks like this:

class Team(Model):
    name = CharField(max_length=50)

    def get_captain(self):
        return PlayerRole.objects.get(team=self).player

class Player(Model):
    first_name = CharField(max_length=50)
    last_name = CharField(max_length=50, blank=True)

    def get_team(self):
        return PlayerRole.objects.get(player=self).team

PLAYER_ROLES = (
    ("Regular", "Regular"),
    ("Captain", "Captain")
    )

class PlayerRole(Model):
    player = OneToOneField(Player, primary_key=True)
    team = ForeignKey(Team, null=True)
    role = CharField(max_length=20, choices=PLAYER_ROLES, default=PLAYER_ROLES[0][0])
    class Meta:
        unique_together = ("player", "team")

It might be slightly less efficient in terms of storage than the suggested workaround, but it avoids the circular dependency and keeps the DB structure clean and clear.
Comments are welcome.