DRF 如何仅将第一个序列化对象返回到视图？

Question

在 DRF 中，有没有办法让单个嵌套图像显示在视图中。在我的示例中，您可以看到列出了 2 张照片。检索和显示第一张照片的最佳解决方案是什么？此视图将显示房屋列表，我不希望显示每张照片，因为可能有一些用户上传了 30 多张照片。

            "url": "http://127.0.0.1:8000/api/v1/listings/1/",
            "address": "8753 sherwood dr apt 111",
            "image_set": [
                {
                    "photo": "http://127.0.0.1:8000/media/listing_images/front-view.png"
                },
                {
                    "photo": "http://127.0.0.1:8000/media/listing_images/image34453.png
                }
            ]
        },


class ImageSerializerForListingDetail(serializers.ModelSerializer):
    photo = serializers.ImageField(use_url=True, allow_empty_file=True)
    class Meta:
        model = Image
        fields = ('photo', )
    def get_image_url(self, listing):
        return listing.photo.url


class ListingListSerializer(serializers.HyperlinkedModelSerializer):
    photo = ImageSerializerForListingDetail(many=True, required=False)
    class Meta:
        model = Listing
        fields = ('url', 'address', 'photo', )


class ListingViewSet(viewsets.ModelViewSet):
    queryset = Listing.objects.all().order_by('id')
    permission_classes = [IsOwnerOrReadOnly, ]
    serializer_classes = {
        'list': ListingListSerializer,
        'retrieve': ListingSerializer
    }
    default_serializer_class = ListingSerializer

    def get_serializer_class(self):
        return self.serializer_classes.get(self.action, self.default_serializer_class)

    def create(self, request, *args, **kwargs):
        serializer = ListingSerializer(data=request.data, files=request.FILES)
        if serializer.is_valid():
            serializer.save()
            return Response(serializer.data, status=status.HTTP_201_CREATED)
        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

我刚刚尝试的当前代码，返回一个空的照片列表.... #

class ImageSerializerForListingDetail(serializers.ModelSerializer):
    photo = serializers.ImageField(allow_empty_file=True)

    class Meta:
        model = Image
        fields = ('photo', )

    def get_image_url(self, listing):
        return listing.photo.url



class ListingListSerializer(serializers.HyperlinkedModelSerializer):
    first_image = ImageSerializerForListingDetail(many=True, required=False)

    class Meta:
        model = Listing
        fields = ('url', 'address', 'first_image', )

    def get_first_image(self, obj):
        first_image = Image.objects.filter(listing=obj).first()
        first_image_serializer = ImageSerializerForListingDetail(first_image)
        return first_image_serializer.data

Answer 1

您只能将第一项传递给您的序列化程序：

def get_queryset(self):
    return  Listing.objects.all().order_by('id').first() if self.action == 'retrieve' else Listing.objects.all().order_by('id')

Answer 2

由于我不太确定您的模型如何以及您想展示的第一张照片（例如最新上传的、首次上传的、最新的 id）。我将使用一个通用示例来解释解决方案。

尝试serializers.SerializerMethodField() 自定义您要呈现最新字段的字段。

假设用户模型中有一个组列表，并且您希望在用户的详细信息中显示最新的组 ID。

这是一个例子：

class UserSerializer(serializers.ModelSerializer):
    latest_group_id = serializers.SerializerMethodField()

    def get_latest_group_id(self, obj):
        return Group.objects.filter(user=obj).latest('id').id

由于您想显示照片 url 而不是 id，所以这里是伪代码。

class UserProfileSerializer(serializers.ModelSerializer):
    latest_image = serializers.SerializerMethodField()

    def get_latest_image(self, obj):
        latest_image = Image.objects.filter(user=obj).latest('id')
        latest_image_serializer = ImageSerializerForListingDetail(latest_image)
        # Deal with edge cases, e.g. latest_image_serializer is not valid
        return latest_image_serializer.data