[Answer]-Need to check ForeignKey references a specific object before saving

by

1👍

I would advise to choose another way in determining the winner of the team,
since you have more than one state but winning the game. It could also be an equal score.

The information who won the game is actually indirectly determined by the score of the teams, so try to model the winning game with a property that uses the score to return the winner.

class Game(models.Model):
    away_team = models.ForeignKey(Team, related_name='away_games')
    away_score = models.PositiveSmallIntegerField(blank=True, null=True)
    home_team = models.ForeignKey(Team, related_name='home_games')
    home_score = models.PositiveSmallIntegerField(blank=True, null=True)
    week = models.PositiveSmallIntegerField(validators=[MaxValueValidator(21)])

    @property
    def winner():
        if self.away_score > self.home_score:
            return self.away_team
        elif self.away_score < self.home_score:
            return self.home_team
        else:
            return None

This will eliminate your need for additional validation. If you really want to use validators you should read the django docs about validators first: https://docs.djangoproject.com/en/1.11/ref/validators/

👤Johannes Reichard

0👍

Try this, it should raise an error – if winner is not blank and its not either the away_team or home_team.
Notice its overriding the save method so this validation will be done on Game.save()

class Team(models.Model):
        abbreviation = models.CharField(max_length=5, unique=True)
        location = models.CharField(max_length=100)
        nickname = models.CharField(max_length=100)

class Game(models.Model):
    away_team = models.ForeignKey(Team, related_name='away_games')
    away_score = models.PositiveSmallIntegerField(blank=True, null=True)
    home_team = models.ForeignKey(Team, related_name='home_games')
    home_score = models.PositiveSmallIntegerField(blank=True, null=True)
    week = models.PositiveSmallIntegerField(validators=[MaxValueValidator(21)])
    winner = models.ForeignKey(Team, blank=True, null=True)

    def save(self, *args, **kwargs):
        if not (self.winner and (self.winner == self.away_team or self.winner == self.home_team)):
              raise ValidationError('Winner Error')
        super(Post, self).save(*args, **kwargs)

Since you’re rasing a ValidationError you will need to import ValidationError in your models.py (at the top):

from django.core.exceptions import ValidationError
👤Simar

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