ImageField validation doesn't allow me save a path

[mgaligniana]

Let's say I have this model to save an image:

class Profile(models.Model):
    photo = models.ImageField(max_length=255, null=True, blank=True)

with this serializer:

class ProfileSerializer(serializers.ModelSerializer):
    class Meta:
        model = Profile
        fields = ("id", "photo")

Then I moved to S3 using Presigned Urls: instead of upload a file, the frontend does it for me, and I just do a POST to the Profile's view with photo as the path which S3 gave me (i.e. uploads/photos/foo.png)

I can run profile = Profile.objects.create(photo="uploads/photos/foo.png") successfully and then have access to profile.url (MEDIA_ROOT + path) and profile.name (foo.png).

But when I want create it via POST I get "The submitted data was not a file. Check the encoding type on the form." because it requires send size:

django-rest-framework/rest_framework/fields.py

Line 1513 in 15c613a

file_size = data.size

• Why doesserializers.FileField differ from the models.FileField validation logic?
• What would be the changes required to get the following expected result:
  POST to /api/v1/profiles/ with {"photo": "foo/bar/baz.png}" and then retrieve the profile and get {"id": 1, "photo": "https://s3-bucket.com/foo/bar/baz.png}"

Thank you!

[auvipy]

I think you could try https://django-storages.readthedocs.io/en/latest/backends/amazon-S3.html

[mgaligniana]

Thank you for the answer!

I didn't know about this library! No doubt if I had to do something from scratch I would use that. But in this case I was looking for a solution that doesn't involve add a library or a big change/customization because in my opinon as I'm able to save an ImageField just passing an url, the serializer.ImageField's validation behaviour should be the same, and don't require for an extra param such as size.

I solved in this way: I defined the photo field as read_only and overrided the ViewSet.create method, doing:

def create(self, request, *args, **kwargs):
    serializer = self.get_serializer(data=request.data)
    serializer.is_valid(raise_exception=True)
    instance = serializer.save(photo=request.data.get("photo"))
    instance.save()
    return Response(
        self.serializer_class(instance).data, status=status.HTTP_201_CREATED
    )

What do you think?

Thank you again!

[nachollica]

hi there! i think (not sure) that you can achieve the same result in a more robust way by overriding only the perform_create method, like this:

def perform_create(self, serializer):
    serializer.save(photo=self.request.data.get("photo"))

hope it helps!

[mgaligniana]

Totally agree Nacho 🇦🇷 !

But as in my final code I need to manipulate the instance and the request, and perform_create doesn't return the instance nor receive the request as parameter, I prefer to leave it as it is.

Thank you!