python - Django - 基于外键向序列化器和订单列表添加属性

Question

我正在尝试获取基于外键的数据。 假设我有这些模型:

# models.py
class Player(models.Model):
    name = models.CharField(max_length = 64)

class Game(models.Model):
    score = models.IntegerField()
    player = models.ForeignKey('Player', models.DO_NOTHING, related_name='player', blank=False, null=False)

class InjuredPlayer(models.Model):
    player = models.ForeignKey('Player', models.DO_NOTHING, blank=False, null=False)

我正在使用 REST 框架，所以我有这个序列化器。我想向 Player 序列化器添加一个属性，该属性是所有游戏分数的总和。

# Serializer
class PlayerSerializer(serializers.ModelSerializer):
    # Get the sum of Game scores of the player
    # sum_of_scores = ________________
  class Meta:
    model = Player
    # Use sum_of_scores as a field on the serializer
    fields = ('activity', 'logo', 'sum_of_scores')

然后，想要做的是显示球员列表及其得分总和(如果他们在 InjuredPlayer 上)。所以在我的类里面:

class PlayerList(APIView)

查询集应该类似于:

# I tried this
queryset = Player.objects.filter(injuredplayer__player=id)

如何过滤不在其他表中的对象。 是否可以根据 sum_of_scores 对列表进行排序？如果是这样，怎么办？ 谢谢

Answer 1

如果你想获得序列化器中所有字段的总和，请使用serializerMethodField

from django.db.models import Sum
# also import Game model
class PlayerSerializer(serializers.ModelSerializer):
    sum_of_scores = serializers.SerializerMethodField()

    class Meta:
        model = Player
        fields = ('id', 'name', 'sum_of_scores')

    def get_sum_of_scores(self, obj):
        return Game.objects.filter(player=obj).aggregate(Sum('score'))

注意 您的模型结构不是最佳的，您可以删除 InjuredPlayer 模型，并为 Player 添加新字段，例如 is_injured 。并将其设置为默认 false。而且游戏模型相关的名称应该是“游戏”之类的。以便您可以轻松地反向引用。在您当前的结构中，要获取与玩家相关的所有游戏，您应该调用player.player.all()。如果你把它改为游戏，那就是player.games.all()

所以新的结构应该是

# models.py
class Player(models.Model):
    name = models.CharField(max_length = 64)
    is_injured = models.BooleanField(dafault=False)

class Game(models.Model):
    score = models.IntegerField()
    player = models.ForeignKey('Player', models.DO_NOTHING, related_name='games', blank=False, null=False)

序列化器变成

# Serializer
from django.db.models import Sum
class PlayerSerializer(serializers.ModelSerializer):
    sum_of_scores = serializers.SerializerMethodField()

    class Meta:
        model = Player
        fields = ('id', 'name', 'is_injured', 'sum_of_scores')

    def get_sum_of_scores(self, obj):
        return obj.games.all().aggregate(Sum('score'))