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Django REST Framework:响应中缺少序列化器字段

django-rest-framework django

Anuj TBE · 技术社区 · 7 年前

Django 2.0 和 Django REST Framework .

我有两个模型 contact transaction 如下所示

接触模型

class Contact(models.Model):
    user = models.ForeignKey(User, on_delete=models.CASCADE)
    first_name = models.CharField(max_length=100)
    last_name = models.CharField(max_length=100, blank=True, null=True)

数量给定模型

class AmountGiven(models.Model):
    contact = models.ForeignKey(Contact, on_delete=models.PROTECT)
    amount = models.FloatField(help_text='Amount given to the contact')
    interest_rate = models.FloatField(blank=True, default=None, null=True, help_text='% of interest to be calculated')
    _given_date = models.DateTimeField(
        db_column='given_date',
        default=timezone.now,
        help_text='Date and time when amount was given to the contact'
    )

    def __str__(self):
        return str(self.amount)

    @property
    def given_date(self):
        return self._given_date

    @given_date.setter
    def given_date(self, value):
        self._given_date = value

    @property
    def interest_to_pay(self):
        if self.interest_rate:    
            datetime_diff = datetime.now(get_localzone()) - self.given_date
            days = datetime_diff.days
            duration_in_year = days/365

            simple_interest_amount = (self.amount * duration_in_year * self.interest_rate)/100

            return simple_interest_amount

        return 0

    @property
    def total_payable(self):
        return self.amount + self.interest_to_pay

    @property
    def amount_due(self):
        returned_amount = 0
        for returned in self.amountreturned_set.all():
            returned_amount += returned.amount

        return self.total_payable - returned_amount

和 联系人序列化程序

class ContactSerializer(serializers.HyperlinkedModelSerializer):
    url = serializers.HyperlinkedRelatedField(
        view_name='contacts:detail',
        read_only=True
    )

    user = serializers.CurrentUserDefault()

    amount_due = ReadOnlyField(source='amountgiven__amount_due')

    class Meta:
        model = Contact
        fields = ('url', 'id', 'first_name', 'last_name', 'full_name', 'amount_due')

视图.py

class ContactViewSet(viewsets.ModelViewSet):
    serializer_class = ContactSerializer
    permission_classes = (IsAuthenticated, AdminAuthenticationPermission,)

    def get_queryset(self):
        return Contact.objects.filter(user=self.request.user)

    def perform_create(self, serializer):
        serializer.save(user=self.request.user)

但这里没有 amount_due 和 url /contacts/ 终结点 GET 方法。

2 回复 | 直到 7 年前

Enthusiast Martin 7 年前

您的建模不允许您以所需的方式访问应付金额。

你的 Contact 模型没有 amountgiven 属性。但它确实有 amountgiven_set 您可以使用它来获取给定联系人的给定金额的查询集。

但是可以有多个,所以你需要决定 amount_due

你可以用 SerializerMethodField

class ContactSerializer(serializers.HyperlinkedModelSerializer):
    amount_due = serializers.SerializerMethodField()

    def get_amount_due(self, obj):
         amountgiven = obj.amountgiven_set.first()
         return amountgiven.amount_due

但是,正如我已经提到的,amountgiven_set返回一个queryset,其中可以有多个对象。

first() 就像我的例子一样。

Ehsan Nouri 7 年前

根据您的评论,您需要所有金额的总和(请编辑您的问题)。所以您应该在queryset中使用annotate:

from django.db.models import Sum

def get_queryset(self):
    return Contact.objects.filter(user=self.request.user).annotate(amount_due=Sum('amountgiven_set__amount'))

并将这样的字段添加到序列化程序:

amount_due = serializer.IntegerFiled()