how to add values to a ManyToManyField - django

Question

I have the following model that has a field called who_can_see and I don't know how to add data to this filed nor the type of data (dictionary, array...)
#modles.py
class Author(models.Model):
name = models.CharField(max_length=200)
added_by = models.ForeignKey(
settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
created_date = models.DateTimeField(default=timezone.now)
def __str__(self):
return self.name
class Book(models.Model):
title = models.CharField(max_length=200)
description = models.CharField(max_length=300)
author = models.ForeignKey(Author, on_delete=models.CASCADE)
added_by = models.ForeignKey(
settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
created_date = models.DateTimeField(default=timezone.now)
#🔴
who_can_see = models.ManyToManyField(
settings.AUTH_USER_MODEL, related_name='tweet_user', blank=True)
def __str__(self):
return self.title
you can see here where i add the 🔴, I am trying to who_can_see= [author, payload["who_can_see"]] so I expected the field who_can_see to be an array but when I make the POST request i got 500 error
#api_view(["POST"])
#csrf_exempt
#permission_classes([IsAuthenticated])
def add_book(request):
print({"request.data": request.data})
payload = request.data
user = request.user
try:
author = Author.objects.get(id=payload["author"])
book = Book.objects.create(
title=payload["title"],
description=payload["description"],
added_by=user,
author=author,
# who_can_see= [author, payload["who_can_see"]] # 🔴
)
serializer = BookSerializer(book)
return JsonResponse({'books': serializer.data}, safe=False, status=status.HTTP_201_CREATED)
except ObjectDoesNotExist as e:
return JsonResponse({'error': str(e)}, safe=False, status=status.HTTP_404_NOT_FOUND)
except Exception:
return JsonResponse({'error': 'Something terrible went wrong'}, safe=False, status=status.HTTP_500_INTERNAL_SERVER_ERROR)

Answer 1

You should first create the book and then add the who_can_see property. Like the example on the documentation
You are almost good in your case. It would look like :
def add_book(request):
print({"request.data": request.data})
payload = request.data
user = request.user
try:
author = Author.objects.get(id=payload["author"])
book = Book.objects.create(
title=payload["title"],
description=payload["description"],
added_by=user,
author=author,
)
book.who_can_see.add(author)
serializer = BookSerializer(book)
return ...
EDIT : I realized that your model is not coherent with your view. Why do you link who_can_see to AUTH_USER_MODEL and not Author ? According to your view, your model should be :
who_can_see = models.ManyToManyField(Author,related_name='tweet_user', blank=True)