Returning MultipleObjects using get() django

Question

I wish to return MultipleObjects but I'm not sure how as I keep getting this error:

MultipleObjectsReturned at /clubs/
get() returned more than one Player -- it returned 2!

I want it to return a list of all the players that belong to the club but it only returns one (if I remove all the other players from my database but when I add the rest of the team it throws this error) I'm not sure how to make get return multiple objects.

models.py

class Club(models.Model):
    name = models.CharField(max_length=4096)
    abbreviation = models.CharField(max_length=4096)
    def __str__(self):
        if self.player:
            return self.player.name
        return self.name

class Player(models.Model):
    name = models.CharField(max_length=4096)
    age = models.IntegerField()
    goals = models.IntegerField()
    club = models.OneToOneField(Club, null=True, related_name='player')

    def __str__(self):
        return self.name

views.py

class ClubViewSet(viewsets.ModelViewSet):
    queryset = Club.objects.order_by('name')
    serializer_class = ClubSerializer

class PlayerViewSet(viewsets.ModelViewSet):
    queryset = Player.objects.order_by('name')
    serializer_class = PlayerSerializer

serializer.py

class ClubSerializer(serializers.HyperlinkedModelSerializer):
   player = serializers.HyperlinkedRelatedField(
      many=False,
      read_only=True,
      view_name='player-detail'
   )
   class Meta:
      model = Club
      fields = ('url','name', 'abbreviation','player')

class PlayerSerializer(serializers.HyperlinkedModelSerializer):
   class Meta:
      model = Player
      fields = ('url', 'name', 'age', 'goals')

@SteinarLima that's not very helpful in this case -- there is no get() in the OPs code. — Alasdair
– Alasdair, Commented Apr 1, 2016 at 10:33

Alasdair · Accepted Answer · 2016-04-01 11:14:17Z

3

You have a one to one field from player to club.

class Player(models.Model):
    club = models.OneToOneField(Club, null=True, related_name='player')

You'll also need to change your club's __str__ method, because it currently uses self.player. I suggest you use the club's name rather than including all the players' names.

class Club(models.Model):
    ...
    def __str__(self):
        returns self.name

This means that each player belongs to one club, and each club belongs to one player.

It would make more sense to use a foreign key instead. That means each player belongs to one club, but many players can belong to the same club.

class Player(models.Model):
    club = models.ForeignKey(Club, null=True, related_name='players')

You'll have to create a migration and run it after making this change.

Then update your serializers to support multiple players.

class ClubSerializer(serializers.HyperlinkedModelSerializer):
    player = serializers.HyperlinkedRelatedField(
        many=True,
        read_only=True,
        view_name='player-detail'
    )
    ...

edited Apr 1, 2016 at 11:14

answered Apr 1, 2016 at 10:30

Alasdair

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3 Comments

TheRapture87 Over a year ago

coercing to Unicode: need string or buffer, NoneType found I get this error now

TheRapture87 Over a year ago

Sorry, I forgot that now I had to change str to get_queryset.

Alasdair Over a year ago

I wouldn't recommend including the players in the __str__ method. Using return self.name might be a better idea.

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