Making Serializers output full GET representation while POSTing with PK's only

[Mike C Leach]

I have a model Vote:

class Vote(models.Model):

user = models.ForeignKey(User)

What I'm trying to achieve is a GET representation that has selected user details available, along with POST requests to create a vote that only require the pk of the user in question. Currently POST requests result in an error about missing fields on the user object.

I.E. GET /votes/1/ should return

{

"user": {

            "pk": 2, 

            "username": "brobot"

    }, 

    "pk": 1

}

while I should be able to create a new vote via POST /votes/ with data

{ "user":2 }

Do I intercept the request before validation and use the User.objects.get(pk=user_pk) to get a fully formed object, and then load that into request.DATA and allow validation and saving to continue? Or am I misunderstanding how to write the serializer and there is an easier way to define what's minimally acceptable to create via POST versus the more complete representation obtained via GET? I assume it would related to using PrimaryKeyRelatedField but there is a paucity of examples for PKField usage versus HyperlinkedFields, especially relating to nested objects. Here is my current serializer code.

Current Serializer code:

class UserSerializer(serializers.ModelSerializer):

    pk = serializers.Field()

    

    class Meta:

        model = User

        fields = ('pk', 'username',)

class VoteSerializer(serializers.ModelSerializer):

    pk = serializers.Field()

    user = UserSerializer()

    

    class Meta:

        model = Vote

        fields = ( 'user', 'pk',)

Thanks for any assistance you can provide.