DRF SerializerMethodField not getting called - django

Question

This is my serializer:
class MetaDataSerializer(serializers.Serializer):
bg_colors = ColorSerializer(Color.objects.all(), many=True)
button_choices = serializers.SerializerMethodField()
class Meta:
fields = ('bg_colors', 'button_choices')
def get_button_choices(self, obj):
return {
'save': 1, 'continue': 2, 'cancel': 3, 'back': 4
}
I'm calling this serializer from my view like this:
class MetaDataView(RetrieveAPIView):
serializer_class = MetaDataSerializer
def get(self, request, *args, **kwargs):
return Response(self.get_serializer().data)
In the response I'm getting only the bg_colors field. The other field is absent from response, and its get_field method is also not called.
What am I doing wrong here?

Answer 1

Instead of passing the Colors queryset directing in serializer definition, pass it from your viewset.
Make this changes:
In serializer :-
class MetaDataSerializer(serializers.Serializer):
bg_colors = ColorSerializer(many=True)
button_choices = serializers.SerializerMethodField()
class Meta:
fields = ('bg_colors', 'button_choices')
def get_button_choices(self, obj):
return {
'save': 1, 'continue': 2, 'cancel': 3, 'back': 4
}
In view :-
class MetaDataView(RetrieveAPIView):
serializer_class = MetaDataSerializer
def get(self, request, *args, **kwargs):
final_data = {"bg_colors": Colors.objects.all()}
return Response(self.get_serializer(final_data).data)

Answer 2

You're not validating your data, you can only access the serializer.initial_data right now, which does not include the custom serializer fields that you've added. You must make a serializer instance first and then check if serializer.is_valid() and then you'll be able to access the custom serializer fields. Remember you can access the serializer data before validating by using serializer.initial_data (here serializer is the serializer instance name), after validation and before saving or inside if serializer.is_valid(): as serializer.validated_data and after saving the validated data as serializer.data
serializer = MetaDataSerializer(request.data)
print(serializer.initial_data)
if serializer.is_valid(raise_exception=True):
print(serializer.validated_data)
serializer.save()
print(serializer.data)
return Response({'data': serializer.data}, status=status.HTTP_200_OK)
now if it got validated without raising any errors then serializer.data will have data saame as the validated_data and if it does not get validate then it will have data same as serializer.initial_data