我想使用嵌套的序列化器字段分组,并在其他字段上计算一些聚合函数
我的模型课程:
class Country(models.Model):
code = models.CharField(max_length=5, unique=True)
name = models.CharField(max_length=50)
class Trade(models.Model):
country = models.ForeignKey(
Country, null=True, blank=True, on_delete=models.SET_NULL)
date = models.DateField(auto_now=False, auto_now_add=False)
exports = models.DecimalField(max_digits=15, decimal_places=2, default=0)
imports = models.DecimalField(max_digits=15, decimal_places=2, default=0)
我的序列化程序类:
class CountrySerializers(serializers.ModelSerializer):
class Meta:
model = Country
fields = '__all__'
class TradeAggregateSerializers(serializers.ModelSerializer):
country = CountrySerializers(read_only=True)
value = serializers.DecimalField(max_digits=10, decimal_places=2)
class Meta:
model = Trade
fields = ('country','value')
我想发送import或export作为查询参数,并对其应用聚合(avg),由不同的国家显示
我的观点类:
class TradeAggragateViewSet(viewsets.ModelViewSet):
queryset = Trade.objects.all()
serializer_class = TradeAggregateSerializers
def get_queryset(self):
import_or_export = self.request.GET.get('data_type')
queryset = self.queryset.values('country').annotate(value = models.Avg(import_or_export))
return queryset
我希望以如下格式获取数据:
[
{
country:{
id: ...,
code: ...,
name: ...,
},
value:...
},
...
]
但在国家/地区序列化程序上出错
AttributeError: Got AttributeError when attempting to get a value for field `code` on serializer `CountrySerializers`.
The serializer field might be named incorrectly and not match any attribute or key on the `int` instance.
Original exception text was: 'int' object has no attribute 'code'.
我找到了解决办法。实际上,serializer类中的to_表示只获取了国家的id,而不是其对象,因此我重写to_表示为:
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