multiple ManyToOne relations serializer - django

Question

sorry my english is not good.
Get request book_id(pk)
How do I serialize ManyToOne fields using BookSerializer to retrieve something
class Book(TimeStampedModel):
name = models.CharField(max_length=25, null=False)
owner = models.ForeignKey(User, on_delete=models.DO_NOTHING,unique=True)
...
class Meta:
db_table = 'books'
class BookMember(TimeStampedModel):
user = models.ForeignKey(User, on_delete=models.DO_NOTHING, null=False)
book = models.ForeignKey(Book, on_delete=models.CASCADE, null=False)
class Meta:
db_table = 'book_member'
class User(AbstractBaseUser, PermissionsMixin):
username = models.CharField(max_length=20, unique=True)
email = models.EmailField(verbose_name=_('email'))
...
class Meta:
db_table = 'user'
class BookSerializer(serializers.ModelSerializer):
user = UserDetailSerializer(read_only=True, many=True, required=False)
owner = UserDetailSerializer(read_only=True, many=True, required=False)
class Meta:
model = Book
fields = '__all__'
I need to book retrieve
class BookViewSet(ModelViewSet):
permission_classes = [AllowAny]
queryset = Book.objects.all()
serializer_class = BookSerializer
renderer_classes = [JSONRenderer]
def retrieve(self, request, *args, **kwargs):
instance = get_object_or_404(self.queryset, many=True)
serializer = self.get_serializer(instance)
return serializer.data

Answer 1

You can span a ManyToManyField [Django-doc] over you BookMember model:
from django.conf import settings
class Book(TimeStampedModel):
# …
owner = models.OneToOneField(
settings.AUTH_USER_MODEL,
on_delete=models.DO_NOTHING
)
members = models.ManyToManyField(
settings.AUTH_USER_MODEL,
through='BookMember'
)
# …
class Meta:
db_table = 'books'
class BookMember(TimeStampedModel):
user = models.ForeignKey(
settings.AUTH_USER_MODEL,
on_delete=models.DO_NOTHING
)
book = models.ForeignKey(
Book,
on_delete=models.CASCADE
)
class Meta:
db_table = 'book_member'
Then you can serialize with:
class BookSerializer(serializers.ModelSerializer):
user = UserDetailSerializer(read_only=True, many=True, required=False)
members = UserDetailSerializer(read_only=True, many=True, required=False)
class Meta:
model = Book
fields = '__all__'
Note: It is normally better to make use of the settings.AUTH_USER_MODEL [Django-doc] to refer to the user model, than to use the User model [Django-doc] directly. For more information you can see the referencing the User model section of the documentation.
Note: Usually it is better to work with a OneToOneField [Django-doc]
instead of a ForeignKey that has unique=True. A OneToOneField is a ForeignKey with unique=True and some small
modifications: for example it uses by default the name of the model in lowercase as
related_name=… [Django-doc]
and makes accessing the relation in reverse more convenient since that does not require a manager in between.
Note: Specifying null=False [Django-doc] is not necessary: fields are by default not NULLable.