如何在Django rest框架中序列化不同的queryset？

Question

我有一个模型处理意大利的增值税税率。有三种类型的费率：'序号'，'里多塔'，'最低'每种类型的费率可以根据一个日期存储多个值。例如，普通增值税的现行税率为22%，已于2013年10月1日设定，但税率随时间变化，我需要存储变化并根据特定日期检索三个税率。你知道吗

描述利率的模型称为AliquoteIVA。我使用自定义管理器检索截至今天的当前费率，或提供特定日期：

class AliquoteIVAManager(models.Manager):
    def current(self, data):
        return self.filter(data__lte=data) \
                    .order_by('descrizione', '-data') \
                    .distinct('descrizione')


class AliquoteIVA(models.Model):
    """ Modello delle aliquote IVA """
    data = models.DateField(
        blank = False,
    )

    descrizione = models.CharField(
        blank = False,
        max_length = 1,
        default = IVA.IVA_ORDINARIA,
        choices = IVA.IVA_TIPOLOGIA_CHOICES,
    )

    aliquota = models.DecimalField(
        blank = False,
        null = False,
        default = '0',
        max_digits=19,
        decimal_places = 2,
        validators = [MinValueValidator(0.0)],
    )

    objects = AliquoteIVAManager()

    def __str__(self):
        str_aliquota = "{0:.2f}".format(self.aliquota).replace('.', ',')

        return "IVA {descrizione} al {aliquota}% in vigore dal {data}".format(
            descrizione=self.get_descrizione_display(),
            aliquota=str_aliquota,
            data=self.data
            )

    class Meta:
        ordering = ('-data', 'aliquota',)
        verbose_name = 'Aliquota IVA'
        verbose_name_plural = 'Aliquote IVA'

我测试了查询集，一切正常：

AliquoteIVA.objects.all()将返回：

<QuerySet [
  <AliquoteIVA: IVA Ordinaria al 26,50% in vigore dal 2021-01-01>, 
  <AliquoteIVA: IVA Ridotta al 13,00% in vigore dal 2020-01-01>,
  <AliquoteIVA: IVA Ordinaria al 25,20% in vigore dal 2020-01-01>,
  <AliquoteIVA: IVA Minima al 4,00% in vigore dal 2013-10-01>,
  <AliquoteIVA: IVA Ridotta al 10,00% in vigore dal 2013-10-01>,
  <AliquoteIVA: IVA Ordinaria al 22,00% in vigore dal 2013-10-01>,
  <AliquoteIVA: IVA Ordinaria al 20,00% in vigore dal 1997-10-01>,
  <AliquoteIVA: IVA Ordinaria al 19,00% in vigore dal 1988-08-01>,
  <AliquoteIVA: IVA Ordinaria al 18,00% in vigore dal 1982-08-05>
]>

AliquoteIVA.objects.current('2019-10-17')将返回：

<QuerySet [
  <AliquoteIVA: IVA Minima al 4,00% in vigore dal 2013-10-01>,
  <AliquoteIVA: IVA Ordinaria al 22,00% in vigore dal 2013-10-01>,
  <AliquoteIVA: IVA Ridotta al 10,00% in vigore dal 2013-10-01>
]>

一切都按预期工作，但我需要设置一个序列化程序和一些api端点，以便在客户机中使用这些速率。你知道吗

AliquoteIVA的序列化程序非常简单：

class AliquoteIVASerializer(serializers.ModelSerializer):
    """
    Serializer per le aliquote IVA
    """
    class Meta:
        model = AliquoteIVA
        fields = '__all__'
        read_only_fields = [
            'id'
            ]

我设置了两个视图：

• 第一个AliquoteIVAViewset将为凝乳率提供api端点。你知道吗
• 最后一个CurrentAliquoteIVAView将只提供一个通用的只读列表api视图来显示当前的速率。你知道吗

class AliquoteIVAViewset(viewsets.ModelViewSet):
    """
    API endpoint per le aliquote IVA
    """

    queryset = AliquoteIVA.objects.all()
    serializer_class = AliquoteIVASerializer
    permission_classes = [permissions.IsAuthenticatedOrReadOnly]
    filter_backends = [filters.SearchFilter]
    search_fields = ['descrizione']


class CurrentAliquoteIVAView(generics.ListAPIView):
    """
    API endpoint per vedere le aliquote IVA correnti in data odierna
    o in base a una data specifica (Y-m-d)
    """

    permission_classes = [permissions.IsAuthenticatedOrReadOnly]
    filter_backends = [filters.SearchFilter]
    search_fields = ['descrizione']

    def get(self, request, data=None, format=None):
        qdata = data if data is not None else datetime.today()

        queryset = AliquoteIVA.objects.current(qdata)
        return Response(queryset)

第一个视图由URL中的路由器处理，第二个视图在URL中显式设置，需要参数data

router = routers.DefaultRouter()
router.register(r'aliquote/iva', views.AliquoteIVAViewset)


aliquote_iva_patterns = [
    path('', views.CurrentAliquoteIVAView.as_view()),
    path('<str:data>', views.CurrentAliquoteIVAView.as_view()),
]


urlpatterns = [
    path('aliquote/iva/corrente/', include(aliquote_iva_patterns)),
    path('', include(router.urls))
]

第一个视图（viewset）按预期工作，但当我试图到达api端点以显示当前速率列表时，django会引发一个错误：

Exception Type: TypeError
Exception Value:    
Object of type 'AliquoteIVA' is not JSON serializable

---

为什么AliquoteIVA.objects.current('2019-10-17')是不可序列化的对象？你知道吗

如何序列化current查询集？你知道吗

Answer 1

通过定义get，您绕过了DRF的所有功能。特别是，您没有调用序列化程序，序列化程序负责将对象转换为可序列化的形式。你知道吗

这个逻辑应该进入get_queryset，而不是get。你知道吗

class CurrentAliquoteIVAView(generics.ListAPIView):
    permission_classes = [permissions.IsAuthenticatedOrReadOnly]
    filter_backends = [filters.SearchFilter]
    search_fields = ['descrizione']
    serializer_class = AliquoteIVASerializer

    def get_queryset(self):
        qdata = self.kwargs.get('data', datetime.today())
        queryset = AliquoteIVA.objects.current(qdata)
        return queryset