How to customize fields in django rest framework serializer

Question

I want to create a new record in database, I set a model like below:

class FooModel(models.Model)
    subject_key= models.CharField(max_length=2)
    subject= modeels.CharField(max_length=100)

What I want to do is this: field 'subject_key' should be given by the client, and using the subject_key, the server will find value 'subject' and put it in the database.

So I tried to use ModelSerializer to create a new record.

class FooSerializer(serializers.ModelSerializer):

    class Meta:
        model = FooModel

    def get_subject(self, obj):
        if obj.subject == 'SO':
            return 'Stack Overflow'
        else:
            return 'Nothing in here'

and main running code inside view rest api is:

class FooView(APIView):
    def post(self, request, *args, **kwargs):
        serializer = FooSerializer(data=request.data)
        if serializer.is_valid(raise_exception=True)
            serializer.save()
            foo = serializer.data

I checked it successfully create a new record in database, but the new record has NULL with the column 'subject'

What should I do to dynamically set the field value inside serializer?

Answer 1

you declare your subject field in serializer as method field, it always read only ( serializermethodfield ), you can rename your filed for example:

class FooSerializer(serializers.ModelSerializer):
    class Meta:
        model = FooModel

    def get_var_subject(self, obj):

in this way you will have tree fields in your seriaizer 'subject', 'subject_key', 'var_subject'

OR you can add your mehod to the model and use to_representation

def to_representation(self, instance):
    representation = super(FooSerializer, self).to_representation(instance)
    representation['subject'] = instance.get_subject()
    return representation

OR use field to_representation example for related filed but i hope you can use it

OR you need to override save method

Answer 2

you can try this

def post(self, request, *args, **kwargs):
        request.data['subject_key'] = request.data['subject']
        serializer = FooSerializer(data=request.data)
        if serializer.is_valid(raise_exception=True)
            serializer.save()
            foo = serializer.data