What is the easiest way to get custom serialized m

I am looking for an easy way to subclass rest_framework.serializers.ModelSerializer from Django REST framework so that it serializes to a special dictionary for foreign key models fields with the name of the model class and the id value instead of just an integer / primary key. This should work for different models.

# models.py
class Author(models.Model):
    name = models.CharField(max_length=255)

class Book(models.Model):
    book_written_by = models.ForeignKey(Author)

class Song(models.Model):
    song_written_by = models.ForeignKey(Author)

# serializers.py
class CustomSerializer(serializers.ModelSerializer):
    # What to do here? #

class BookSerializer(CustomSerializer):
    class Meta:
        model = Book

class SongSerializer(CustomSerializer):
    class Meta:
        model = Song

I would like to get the following result:

kleist = Author.objects.create(name='Kleist')
some_book = Book.objects.create(author=kleist)
BookSerializer(some_book).data == {'id': 1, 'book_written_by': {'Author': 1}}  # Returns True

I tried to override get_related_field() and changed PrimaryKeyRelatedField to a CustomPrimaryKeyRelatedField and there I tried to override to_native() but I don't have access to the model field and its object itself but only to the pk value.

What you need is certainly achievable, but it is really breaking convention so personally I'd vote against doing so. Nevertheless, a way to achieve what you need is to use a SerializerMethodField:

class BookSerializer(serializers.ModelSerializer):
    book_written_by = serializers.SerializerMethodField('get_author')

    class Meta:
        model = User

    def get_author(self, obj):
        return {'Author': obj.book_written_by.pk}

This would return the exact output you wanted. If you decide to stick with the conventions, I'd prefer an output like this:

{'id': 1, 'book_written_by': {'id': 1, 'name': 'somebody'}}

The following serializer would return that for you:

class AuthorSerializer(serializers.ModelSerializer):
    class Meta:
        model = Author
        fields = ('id', 'name')

class BookSerializer(serializers.ModelSerializer):
    book_written_by = AuthorSerializer()