Using django rest framework, how to add new nested child object for existing parent object - django-rest-framework

Question

I am trying to build a data storage for time series data, for this I have created nested objects Coin and Data, where Coin is parent object and contains Data entries that each data entry is individual object. at this moment my code creates nested object Coin[Data] as I build create function within CoinSerializer, but I could not use proper method to add/create child object within existing Coin object
In my python virtual environment I've been using django 2.1.4 drf 3.9 and python 3.6.. also as a backend db engine for my project I got mongodb and use djongo 1.2 to maintain it
Any suggested idea or way for my problem would be greatly appreciated, as its my first post ever and sorry for any Inappropriate style..
models.py
class Coin(models.Model):
coin_name = models.CharField(max_length=100,blank=True)
class Data(models.Model):
coin = models.ForeignKey(Coin, related_name='data', on_delete=models.CASCADE,blank=True)
date = models.DateField(("Date"),blank=True)
open = models.FloatField(null=True, blank=True)
high = models.FloatField(null=True, blank=True)
low = models.FloatField(null=True, blank=True)
close = models.FloatField(null=True, blank=True)
class Meta:
unique_together = ('coin', 'date',)
ordering = ['date']
def __unicode__(self):
return '%d: %d %d %d %d' % (self.date, self.open, self.high,
self.low, self.close)
serializers.py
class DataSerializer(serializers.ModelSerializer):
class Meta():
model = models.Data
fields = ('coin_id','pk','id','date','open','high','low','close')
class CoinSerializer(serializers.ModelSerializer):
data = DataSerializer(many=True)
class Meta:
model = models.Coin
fields = ('pk','id','coin_name', 'data')
def create(self, validated_data):
data = validated_data.pop('data')
coin = models.Coin.objects.create(**validated_data)
models.Data.objects.create(coin=coin, **data[0])
return coin
my result is kind of this
{
"pk": 101,
"id": 101,
"coin_name": "ripple",
"data": [
{
"coin_id": 101,
"pk": 56,
"id": 56,
"date": "2016-12-25",
"open": 4036.0,
"high": 4101.0,
"low": 3983.0,
"close": 4065.0
}
]
},
and expect to consist lots of data objects which I will add by the time in existing coin object
{
"pk": 101,
"id": 101,
"coin_name": "ripple",
"data": [
{
"coin_id": 101,
"pk": 56,
"id": 56,
"date": "2016-12-25",
"open": 4036.0,
"high": 4101.0,
"low": 3983.0,
"close": 4065.0
}
{
"coin_id": 102,
"pk": 57,
"id": 57,
"date": "2016-12-26",
"open": 4065.0,
"high": 4189.0,
"low": 3967.0,
"close": 4075.0
}
...
...
]
},

Answer 1

You're going about it the wrong way. You should instead make another endpoint for Data too. There you can create data and pass the id of the parent coin. Using the nested architecture is only meaningfull when you're creating both the coin and the data at the same time. In this case, just use a data endpoint to create data while passing the id of the coin
EDIT: BULK CREATE
And just to throw a little light on how to implement bulk create for several Data objects - you will need to imlement it using a loop as model.objects.create() excpects data for a single object. You could use bulk_create but it has a lot of caveats, so I would use a loop

Answer 2

try change your input data with more than one item in array like example:
data = [{'date': '2016-12-25', 'high': 4101.0, 'open': 0.0, 'low': 3983.0, 'close': 4065.0}, {'date': '2016-12-26', 'high': 4101.0, 'open': 0.0, 'low': 3983.0, 'close': 4065.0}]
This example have one more item in array data.
And change this line:
coin = models.Coin.objects.create(**validated_data)
models.Data.objects.create(coin=coin, **data[0])
to
coin = models.Coin.objects.create(**validated_data)
for item_data in data:
models.Data.objects.create(coin=coin, **item_data)
This will create some Data with FK is Coin created.

Answer 3

This is how I did it.. Inside my viewset.ModelViewSet implementation In my case.. The parent class contains a list of manyToMany objects. Im posting new objects in the manyToMany..> Creating them.. then reinserting the IDs into the post data and calling the base class. Worked out pretty simple.. and I like it's contained in the view. Im newer to Django however.. but this worked for me.
class CaseDeepViewSet(viewsets.ModelViewSet):
permission_classes = (IsAuthenticated,)
queryset = Case.objects.all().order_by('-id')
def get_serializer_class(self):
if self.request.method in ['GET']:
return CaseDeepSerializer
return CaseSerializer
def create(self, request):
print('IM here: ')
print(request.data)
case_interactions = request.data.pop('new_case_interactions')
listCreatedInteractions = []
for interaction in case_interactions:
print("interaction", interaction)
interaction['issara_staff'] = obj = IssaraUser.objects.get(pk=interaction.get('issara_staff'))
listCreatedInteractions.append(CaseInteraction.objects.create(**interaction).id)
request.data['case_interactions'] = listCreatedInteractions
return super().create(request)