django - get() returned more than one topic

Question

When I tried to relate an attribute with another one which has an M to M relation I received this error:

get() returned more than one

Answer 1

To add to CrazyGeek's answer, get or get_or_create queries work only when there's one instance of the object in the database, filter is for two or more.

If a query can be for single or multiple instances, it's best to add an ID to the div and use an if statement e.g.

def updateUserCollection(request):
    data = json.loads(request.body)
    card_id = data['card_id']
    action = data['action']

    user = request.user
    card = Cards.objects.get(card_id=card_id)

    if data-action == 'add':
        collection = Collection.objects.get_or_create(user=user, card=card)
        collection.quantity + 1
        collection.save()

    elif data-action == 'remove':
        collection = Cards.objects.filter(user=user, card=card)
        collection.quantity = 0
        collection.update()

Note: .save() becomes .update() for updating multiple objects. Hope this helps someone, gave me a long day's headache.