Django REST Framework: accepting multiple POSTed objects with a list_route

Question

I have a ModelViewSet with an extra list_route to handle GET/POST for a certain list of objects:

class PickViewset(viewsets.ModelViewSet):

  queryset = Pick.objects.all()
  serializer_class = PickSerializer

  def get_queryset(self):
   #gets the correct queryset

  @list_route(methods=['get', 'post'])
  def update_picks(self, request, league, week, format = None):
    if request.method == 'POST':
      #process/save objects here
    else:
      #otherwise return the requested list

Thanks to the answer on my earlier question, this action can successfully handle a GET request as well as POST- however, when I try to POST more than one object, I get a JSON error:

"detail": "JSON parse error - Extra data: line 90 column 6 - line 181 column 2 (char 3683 - 7375)"

Where the specified location corresponds to the end of the first object. How can I change update_picks to handle a list of objects as well? Also, if this request may be a mix of new and updated existing objects, should I even be using POST for all, or just handle each POST/PUT on a per-object basis?

I considered adding a CreateModelMixin to the Viewset, however it can already create- but just one object. The ListCreateAPIView seems to be similar- it doesn't have an inherent list creation, but rather just the CreateModelMixin and ListModelMixin- both of which I think are provided by default when using a ModelViewset.

Maybe related: stackoverflow.com/questions/21439672/… and stackoverflow.com/questions/14666199/… — ilse2005
– ilse2005, Commented Feb 16, 2016 at 13:58
Thanks- I had taken a look at these as they seem similar, however I believe both issues deal more with how to serialize multiple objects with DRF. In my case, if I post more than 1 object, I can't even step into the provided code because the JSON error is returned before it makes it into the viewset. The first posted used a ListCreateAPIView, however I think the mixins it includes are already included with a ModelViewset- but perhaps I'm wrong on that. — dkhaupt
– dkhaupt, Commented Feb 16, 2016 at 14:18

Community · Accepted Answer · 2017-05-23 10:28:00Z

1

I think you have to overwrite the post method (see the question here Django Rest Framework Batch Create) and parse the json on your own using JSONParser().parse()

def post(self, request, *args, **kwargs):
    if request.DATA['batch']:
        json = request.DATA['batchData']
        stream = StringIO(json)
        data = JSONParser().parse(stream)
        request._data = data
    return super(CharacterDatumList, self).post(request, *args, **kwargs)

edited May 23, 2017 at 10:28

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answered Feb 16, 2016 at 14:37

ilse2005

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7 Comments

dkhaupt Over a year ago

With a ModelViewset, though, can post be overwritten? The DRF docs make it sound like that's not the case: A ViewSet class is simply a type of class-based View, that does not provide any method handlers such as .get() or .post(), and instead provides actions such as .list() and .create(). I think the poster of that question could because he used a ListCreateAPIView

ilse2005 Over a year ago

I think you can. But can you post the full traceback to find out in where the error is thrown?

dkhaupt Over a year ago

Well, the error just shows up in the browsable API as the returned JSON from POSTing 2 objects- it's not a Django/DRF error with the bad screen, full traceback, and local variables. This makes me think it's a sort of routing error, but I know it can hit the POST part of the update_picks action- it just isn't getting there with more than 2 objects present. I'm not at home now, but I can provide a screenshot later.

ilse2005 Over a year ago

Could you post the JSON object?

dkhaupt Over a year ago

I'll upvote the answer, but I didn't actually overwrite the POST method- the code worked as structured in my original question, and I'm still not sure if overwriting POST in a Viewset actually works. I think it'd be misleading if I accepted an answer that I didn't actually use- but I am appreciative of your help.

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