DRF - Format Serializer's output from QuerySet - django

Question

I am working with Django Rest Framework by firt time and now I'm trying to get an output like this:
{
"qty": 5,
"total": 20,
"items": [
{
"id": 1,
"name": "name_1"
},
{
"id": 2,
"name": "name_2"
}
]
}
from a Serializer. The result data in output above, came from a queryset. I'd like to work with the queryset inside the serializer class. I've not been able to get results as I want without makeing queries inside the serializer:
class ResSerializer(serializers.Serializer):
qty = serializers.SerializerMethodField()
items = serializers.SerializerMethodField()
total = serializers.SerializerMethodField()
def get_qty(self, obj):
try:
return Model.objects.filter(...)\
.aggregate(qty=Sum('job__long'))\
.get('qty')
except KeyError:
return 0
def get_items(self, obj):
print 'testing'
def get_total(self, obj):
return 0
class Meta:
fields = ('qty', 'items', 'total')
I'm calling Serializer like this:
queryset = Model.objects.filter(...)
serialized = ResSerializer(queryset, many=False, context={'current_user': request.user})
But this is not working as I want. Any sugestion? Thanks.
UPDATE
This is the model I query to:
class Intermediate(models.Model):
partner = models.ForeignKey('partner.Partner')
job = models.ForeignKey(Job)
joined_at = models.DateTimeField(auto_now_add=True)
modified = models.DateTimeField(auto_now=True)
status = models.SmallIntegerField(default=STATUS_ACCEPTED)
reason_index = models.SmallIntegerField('Cancel reason', default=REASON_3)
start_time = models.TimeField(null=True)
end_time = models.TimeField(null=True)
start_date = models.DateField(null=True)
end_date = models.DateField(null=True)
And here's the view:
class ResView(CustomAPIView):
authentication_classes = (CustomTokenAuthentication, )
# permission_classes = (PartnerAuthenticatedOnly, ) # Uncomment this on server
def post(self, request, *args, **kwargs):
try:
queryset = JobPartner.objects.filter(...)
serialized = ResSerializer(queryset, many=False, context={'current_user': request.user})
response_success_object(self.response_dic, serialized.data)
return Response(self.response_dic)
except Exception, e:
print e

Answer 1

To get the items representation, you can use ItemsSerializer which will give the serialized data having id and name.
class ItemsSerializer(serializers.ModelSerializer):
class Meta:
model = MyModel # specify your model
fields = ('id', 'name') # return these 2 fields in the representation
This serializer when dealing with multiple instances will return the serialized data in below fashion.
[
{
"id": 1,
"name": "name_1"
},
{
"id": 2,
"name": "name_2"
}
]
Now, the qty and total fields depends on the queryset and not a particular object of the queryset, it would be better if you compute them separately in your view. Then create a dictionary containing the fields items, qty and total and return it as the response.
class ResView(CustomAPIView):
authentication_classes = (CustomTokenAuthentication, )
# permission_classes = (PartnerAuthenticatedOnly, ) # Uncomment this on server
def post(self, request, *args, **kwargs):
try:
queryset = JobPartner.objects.filter(...)
qty = self.get_qty() # compute the value of qty
total = self.get_total() # compute the value of total
items_serializer = ItemsSerializer(queryset, many=True)
items = items_serializer.data # compute the value of items
return_dict = { # prepare response data
'qty' : qty,
'total': total,
'items': items
}
return Response(return_dict) # return the response
except Exception, e:
print e