Django Rest Framework returns relative path instead of full url with SerializerMethodField

Question

I am experiencing a strange issue. I have been developing an application using Django and DRF along with react in frontend. My app has two models, Place and Cover. Every place has a cover image and here is the database schema.

Image Table

+----+---------------------+----------+----------------------+
| pk |        file         |  title   |     description      |
+----+---------------------+----------+----------------------+
|  1 | /media/my-image.jpg | My Image | My Image Description |
+----+---------------------+----------+----------------------+

Place Table

+----+------+-------+
| pk | code | cover |
+----+------+-------+
|  1 | abcd |     1 |
+----+------+-------+

My operation is simple. I will request for place details using the place code and DRF will return the details. And here is what I wrote initially.

class ImageSerializer(ModelSerializer):
    class Meta:
        model = Image
        fields = ["pk", "file", "title", "description"]

class PlaceDetailSerializer(ModelSerializer):
    cover = ImageSerializer()

    class Meta:
        model = Place
        fields = ["code", "cover"]

class PlaceDetailView(RetrieveAPIView):
    serializer_class = PlaceDetailSerializer
    permission_classes = []
    queryset = Place.objects.filter(deleted=False, published=True)
    lookup_field = 'code'
    lookup_url_kwarg = 'code'

And here is the output of the request

{
    "code": "3469324020",
    "cover": {
        "pk": 13,
        "file": "http://127.0.0.1:8000/media/my-image.jpg ",
        "title": "My Image",
        "description": ""
    }
}

Everything is fine so far. As I wanted the full url of my image and that's exactly what I have got. But the problem occurs when I start using SerializerMethodField()

class PlaceDetailSerializer(ModelSerializer):
    cover = SerializerMethodField()

    def get_cover(self, place):
        return ImageSerializer(place.cover).data

    class Meta:
        model = Place
        fields = ["code", "cover"]

And here is the new response after the changes

{
    "code": "3469324020",
    "cover": {
        "pk": 13,
        "file": "/media/my-image.jpg",
        "title": "My Image",
        "description": ""
    }
}

See? DRF is no longer returning absolute url but relative. I am curious why is that? Is it related to DRF context params??

I have also noticed that the absolute url doesn't work with APIView either.

class PlaceDetailSerializer(ModelSerializer):
    cover = ImageSerializer()

    class Meta:
        model = Place
        fields = ["code", "cover"]


class PlaceDetailView( APIView ):
    serializer_class = PlaceDetailSerializer
    permission_classes = []
    queryset = Place.objects.filter(deleted=False, published=True)
    lookup_field = 'code'
    lookup_url_kwarg = 'code'

    def get(self, request, *args, **kwargs):
        place = Place.objects.get(code=kwargs.get("code"))
        return Response(PlaceDetailSerializer(place).data)

It will also return the relative url as output.

Now I know that there are ways to return full url using get_absolute_url() or other functions. But I am just curious why this isn't working with SerializerMethodField or APIView. I hope if you know, you might be able to help me understand what's going on here.

Paul Kuhle · Accepted Answer · 2020-07-13 18:58:29Z

5

You need to make the request available to the serializer, like so:

return Response(PlaceDetailSerializer(place, context={'request': request}).data)

return ImageSerializer(place.cover, context={'request': request}).data

Normally, Django Rest Framework does this for you, but if you invoke the serializer class manually (e.g. in a MethodField), you have to also pass the request as a context variable.

Check out how the FileField is serialized:

request = self.context.get('request', None)
if request is not None:
     return request.build_absolute_uri(url)
return url

If you don't pass in the request as a context variable, the serializer can't build the absolute URL.

answered Jul 13, 2020 at 18:58

Paul Kuhle

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