Catalog serizalier and field

serializers.py

from catalog import CatalogMember
from collections import OrderedDict
from itertools import chain

from rest_framework.exceptions import APIException
from rest_framework.fields import ReadOnlyField
from rest_framework.serializers import Serializer


class CatalogSerializer(Serializer):
    def __init__(self, *args, **kwargs):
        if not hasattr(self, 'Meta') or not getattr(self.Meta, 'catalog'):
            raise APIException('A catalog instance must be provided.')
        super().__init__(*args, **kwargs)

    def to_representation(self, obj):
        if isinstance(obj, CatalogMember):
            member = obj
        else:
            member = self.Meta.catalog(obj)
        return super().to_representation(member)

    def get_fields(self):
        return OrderedDict(
            (attr, ReadOnlyField())
            for attr in chain(self.Meta.catalog._attrs, ['name'])
            if attr in getattr(self.Meta, 'fields', chain(self.Meta.catalog._attrs, ['name']))
        )


class CatalogField(ReadOnlyField):
    def __init__(self, catalog, *args, display_attr=None, **kwargs):
        self.catalog = catalog
        self.display_attr = display_attr
        super().__init__(*args, **kwargs)

    def to_representation(self, obj):
        if self.display_attr:
            return getattr(self.catalog(obj), self.display_attr)
        else:
            return super().to_representation(vars(self.catalog(obj)))