该项目的目标是创建一个每小时刷新一次的API,其中包含我将每小时从互联网上抓取的一系列游戏的最新下注赔率。返回的JSON的目标结构将是每个游戏作为父对象,而嵌套的子对象将成为按更新日期被抓取的每个制线师的前1条记录。我的理解是,完成此操作的最佳方法是修改ListSerializer中的to_representation函数以返回适当的查询集。
因为我需要父元素的game_id来抓取适当游戏的子元素,所以我试图将game_id从传递的数据中拉出。问题是,当我通过异常查看它包含的内容时,看起来该行已正确填充,但是当我运行完整代码时,我得到列表索引超出范围的异常。
例如。
class OddsMakerListSerializer(serializers.ListSerializer):
def to_representation(self, data):
game = data.all()[0].game_id
#if I put this here it evaluates to 1 which should run the raw sql below correctly
raise Exception(game)
data = OddsMaker.objects.filter(odds_id__in = RawSQL(''' SELECT o.odds_id
FROM gamesbackend_oddsmaker o
INNER JOIN (
SELECT game_id
, oddsmaker
, max(updated_datetime) as last_updated
FROM gamesbackend_oddsmaker
WHERE game_id = %s
GROUP BY game_id
, oddsmaker
) l on o.game_id = l.game_id
and o.oddsmaker = l.oddsmaker
and o.updated_datetime = l.last_updated
''', [game]))
#if I put this here the data appears to be populated correctly and contain the right data
raise Exception(data)
data = [game for game in data]
return data
现在,如果删除这些引发异常,则会得到列表索引超出范围。我最初的想法是,还有其他依赖于作为列表返回的“数据”的东西,因此我创建了列表理解代码段,但这不能解决问题。
所以,我的问题是1)是否有更简单的方法来完成我要去的工作?我没有使用postgres后端,因此无法使用。 2)如果不是,我不清楚传入的是什么实例或预期返回的实例。我已经查阅了文档,看起来好像期望使用字典,这可能是问题的一部分,但是错误消息再次引用了列表。 https://www.django-rest-framework.org/api-guide/serializers/#overriding-serialization-and-deserialization-behavior
我非常感谢您提前了解这里的情况。
编辑:其余的序列化器:
class OddsMakerSerializer(serializers.ModelSerializer):
class Meta:
list_serializer_class = OddsMakerListSerializer
model = OddsMaker
fields = ('odds_id','game_id','oddsmaker','home_ml',
'away_ml','home_spread','home_spread_odds',
'away_spread_odds','total','total_over_odds',
'total_under_odds','updated_datetime')
class GameSerializer(serializers.ModelSerializer):
oddsmaker_set = OddsMakerSerializer(many=True, read_only=True)
class Meta:
model = Game
fields = ('game_id','date','sport', 'home_team',
'away_team','home_score', 'away_score',
'home_win','away_win', 'game_completed',
'oddsmaker_set')
models.py:
class Game(models.Model):
game_id = models.AutoField(primary_key=True)
date = models.DateTimeField(null=True)
sport=models.CharField(max_length=256, null=True)
home_team = models.CharField(max_length=256, null=True)
away_team = models.CharField(max_length=256, null=True)
home_score = models.IntegerField(default=0, null=True)
away_score = models.IntegerField(default=0, null=True)
home_win = models.BooleanField(default=0, null=True)
away_win = models.BooleanField(default=0, null=True)
game_completed = models.BooleanField(default=0, null=True)
class OddsMaker(models.Model):
odds_id = models.AutoField(primary_key=True)
game = models.ForeignKey('Game', on_delete = models.CASCADE)
oddsmaker = models.CharField(max_length=256)
home_ml = models.IntegerField(default=999999)
away_ml = models.IntegerField(default=999999)
home_spread = models.FloatField(default=999)
home_spread_odds = models.IntegerField(default=9999)
away_spread_odds = models.IntegerField(default=9999)
total = models.FloatField(default=999)
total_over_odds = models.IntegerField(default=999)
total_under_odds = models.IntegerField(default=999)
updated_datetime = models.DateTimeField(auto_now=True)
views.py:
class GameView(viewsets.ModelViewSet):
queryset = Game.objects.all()
serializer_class = GameSerializer
谢谢
要回答标题中的问题,传递给instance
的Serializer.to_representation()
是初始化序列化程序时传递的实例
queryset = MyModel.objects.all()
Serializer(queryset, many=True)
instance = MyModel.objects.all().first()
Serializer(data)
通常,您不必从ListSerializer
本身继承。您可以从BaseSerializer
继承,并且在初始化期间每当传递many=True
时,它将自动成为a
ListSerializer`。 You can see this in action here