Django Rest Framework 过滤计算模型属性

抱歉，有一个新手问题。我有以下模型：

class WeightSlip(models.Model):

    grossdate = models.DateTimeField(auto_now=False, auto_now_add=False)
    grossweight = models.DecimalField(max_digits=6, decimal_places=2, default=0)
    taredate = models.DateTimeField(auto_now=False, auto_now_add=False)
    tareweight = models.DecimalField(max_digits=6, decimal_places=2, default=0)
    vehicle = models.CharField(max_length=12)

    @property
    def netweight(self):
        return self.grossweight - self.tareweight

    @property
    def slipdate(self):
        if self.grossdate > self.taredate:
           return grossdate.date()
        else:
           return taredate.date()

序列化器：

class WeightSlipSerializer(serializers.ModelSerializer):

   class Meta:
      model = models.WeightSlip
      fields = ('grossdate', 'grossweight', 'taredate', 'tareweight', 'slipdate', 'netweight', 'vehicle')
      read_only_fields = ('slipdate', 'netweight')

我正在尝试使用django-rest-framework-过滤器 https://github.com/philipn/django-rest-framework-filters过滤计算出的“netweight”和“slipdate”属性：

class WeightSlipFilter(FilterSet):

   class Meta:
       model = WeightSlip
       fields = ('slipdate', 'netweight', 'vehicle')

这给了我一个错误：

TypeError: 'Meta.fields' contains fields that are not defined on this FilterSet: slipdate, netweight

除了将计算字段添加到数据库之外，是否有解决此问题的方法？

提前致谢。

您可以创建自定义过滤器slipdate, netweight这将评估和过滤数据库中的这些字段。为此，您可以使用条件表达式 https://docs.djangoproject.com/en/1.11/ref/models/conditional-expressions/ and F表达 https://docs.djangoproject.com/en/1.11/ref/models/conditional-expressions/

from django.db.models import F, Case, When

class WeightSlipFilter(FilterSet):
    slipdate = DateTimeFilter(method='filter_slipdate')
    netweight = NumberFilter(method='filter_netweight')

    class Meta:
        model = WeightSlip
        fields = ('slipdate', 'netweight', 'vehicle')

    def filter_netweight(self, queryset, value):
        if value:
            queryset = queryset.annotate(netweight=F('grossweight') - F('tareweight')).filter(netweight=value)
        return queryset

    def filter_slipdate(self, queryset, value):
        if value:
            queryset = queryset.annotate(slipdate=Case(When(grossdate__gt=F('taredate'), then=F('grossdate')), default=F('taredate')).filter(slipdate=value)
        return queryset