We Keep Coding

How can I serialize one to many models in Django Rest?

So I have two models Invoice and Items. Invoices can have many Items. Here's how they are defined:
class Invoice(models.Model):
customer_name = models.CharField(max_length = 200, verbose_name='Customer Name')
customer_phone = models.IntegerField(null = True, blank = True, verbose_name='Customer Phone')
customer_address = models.TextField(null = True, blank = True, verbose_name='Customer Address')
invoice_id = models.UUIDField(primary_key = True, unique = True, default=uuid.uuid4, verbose_name='Invoice ID')
invoice_date = models.DateField(auto_now_add=True, verbose_name='Invoice Date')
def __str__(self):
return self.customer_name + ' - ' + str(self.invoice_id)
class Meta:
verbose_name = 'Invoice'
verbose_name_plural = 'Invoices'
class Items(models.Model):
invoice = models.ForeignKey(Invoice, on_delete = models.CASCADE, related_name='invoice')
item_name = models.CharField(max_length = 200, null = False)
item_quantity = models.IntegerField()
item_price = models.IntegerField()
item_id = models.AutoField(primary_key=True)
def __str__(self):
return self.item_name
class Meta:
verbose_name = 'Items'
verbose_name_plural = 'Items'
I want to implement two API endpoints, one to get the list of invoices, and another to get a specific invoice with its items.
For example, /api/ will return all invoices
[
{
"customer_name": "John Doe",
"customer_phone": 111666,
"customer_address": "Palo Alto, California",
"invoice_id": "a8aeb5a8-5498-40fd-9b4f-bb09a7057c71",
"invoice_date": "2022-05-04"
},
{
"customer_name": "Cassian Green",
"customer_phone": 111000,
"customer_address": "2112 Illinois Avenue",
"invoice_id": "7d7b7878-3ffc-4dd2-a60a-fa207c147860",
"invoice_date": "2022-05-04"
},
{
"customer_name": "Chelsea Davis",
"customer_phone": 666777,
"customer_address": "2260 Coplin Avenue",
"invoice_id": "3dda2054-49d7-49dc-9eba-ddc0fdacfd3b",
"invoice_date": "2022-05-04"
},
{
"customer_name": "Derek Elliott",
"customer_phone": 111100,
"customer_address": "3236 Sundown Lane",
"invoice_id": "da112c0d-aff4-43d3-a465-910cc1483fc5",
"invoice_date": "2022-05-04"
}
]
and now if I request a specific invoice with its items, like /api/a8aeb5a8-5498-40fd-9b4f-bb09a7057c71 should return the following response
{
"invoice_id": "a8aeb5a8-5498-40fd-9b4f-bb09a7057c71",
"items": [
{
"item_name": "PC Cabinet",
"item_quantity": 1,
"item_price": 200
},
{
"item_name": "Motherboard",
"item_quantity": 1,
"item_price": 1000
},
{
"item_name": "PSU",
"item_quantity": 1,
"item_price": 300
}
]
}
Here are the serializers:
class ItemSerializer(serializers.ModelSerializer):
class Meta:
model = Items
fields = [
'item_name',
'item_quantity',
'item_price',
]
class InvoiceSerializer(serializers.ModelSerializer):
items = ItemSerializer(many=True, read_only=True)
class Meta:
model = Invoice
fields = [
'customer_name',
'customer_phone',
'customer_address',
'invoice_id',
'invoice_date',
'items'
]
And the views:
#api_view(['GET',])
def InvoiceList(request):
if request.method == 'GET':
queryset = Invoice.objects.all()
serializer_class = InvoiceSerializer(queryset, many=True)
return Response(serializer_class.data)
#api_view(['GET',])
def InvoiceDetail(request, pk):
if request.method == 'GET':
queryset = list(Items.objects.filter(invoice = pk))
serializer_class = ItemSerializer(instance=queryset, many=True)
return Response(serializer_class.data)
The first API endpoint is working as expected but the I need help with implementing the second one. How can I get that nested response?
Thanks.

Your related_name of invoice in Items model is wrong, you should set it as "items" because you are going to call that from Invoice model like that.
Also if you want to have different response from that second API you should change it to use other serializer than InvoiceList:
#api_view(['GET',])
def InvoiceDetail(request, pk):
if request.method == 'GET':
queryset = list(Items.objects.filter(invoice = pk))
serializer_class = InvoiceDetailSerializer(instance=queryset, many=True)
return Response(serializer_class.data)
I changed name of serializer to InvoiceDetailSerializer so you need to create new serializer:
class InvoiceDetailSerializer(serializers.ModelSerializer):
items = ItemSerializer(many=True, read_only=True)
class Meta:
model = Invoice
fields = [
'invoice_id',
'items'
]

you can try something like this. (not tested)
class ItemSerializer(serializers.ModelSerializer):
class Meta:
model = Items
fields = ['item_name', 'item_quantity', 'item_price',]
class InvoiceDetailsSerializer(serializers.ModelSerializer):
items = ItemSerializer(many=True, read_only=True)
class Meta:
model = Invoice
fields = ['id', 'items']
#api_view(['GET',])
def InvoiceDetail(request, pk):
if request.method == 'GET':
invoice = Invoice.objects.get(id=pk)
serializer_class = InvoiceDetailsSerializer(instance=invoice)
return Response(serializer_class.data)

How to add aggregate values in Django Rest Framework ModelViewSets

In my DRF app I have the following model, serializer and view.
models.py
class Log(models.Model):
plant = models.ForeignKey(Plant, on_delete=models.CASCADE)
date_time = models.DateTimeField()
water_consumption = models.PositiveSmallIntegerField()
elec_consumption = models.PositiveSmallIntegerField()
serializers.py
class ConsumptionSerializer(serializers.ModelSerializer):
class Meta:
model = Log
fields = ("water_consumption", "elec_consumption")
views.py
class ConsumptionViewSet(viewsets.ModelViewSet):
permission_classes = [permissions.IsAuthenticated, ]
serializer_class = ConsumptionSerializer
def get_queryset(self):
# Get params from url
start_date = self.request.query_params.get('start_date')
end_date = self.request.query_params.get('end_date')
# Make sure params are not null
if start_date is not None and end_date is not None:
queryset = queryset.filter(date_time__range=[start_date, end_date])
return queryset
else:
raise ValidationError({"ERROR": ["No params found in url"]})
This works and it outputs something like this in JSON:
[
{
"water_consumption": 1,
"electrical_consumption": 1
},
{
"water_consumption": 1,
"electrical_consumption": 1
},
{
"water_consumption": 1,
"electrical_consumption": 1
},
]
What I would like to achieve is to receive some aggregated data alongside those data, like this:
{
"total_water_consumption": 3,
"total_elec_consumption": 3,
"detailed_logs": [{
"water_consumption": 1,
"electrical_consumption": 1
},
{
"water_consumption": 1,
"electrical_consumption": 1
},
{
"water_consumption": 1,
"electrical_consumption": 1
}]
}
How should I customise the queryset to have the total values added?
Thank you in advance.

You can do it with SerializerMethodField in your serializer file
Docs in : https://www.django-rest-framework.org/api-guide/fields/#serializermethodfield
And you can access request in serializer as context:
from django.db.models import Sum
class ConsumptionSerializer(serializers.ModelSerializer):
total_water_consumption = serializers.SerializerMethodField()
total_elec_consumption = serializers.SerializerMethodField()
class Meta:
model = Log
fields = ("water_consumption", "elec_consumption")
def get_total_water_consumption(self, obj):
request = self.context['request']
query_params = request.query_params.get(...)
return Log.objects.filter(...).aggregate(Sum('water_consumption')).get('water_consumption__sum')
def get_total_elec_consumption(self, obj):
request = self.context['request']
query_params = request.query_params.get(...)
return Log.objects.filter(...).aggregate(Sum('elec_consumption')).get('elec_consumption__sum')

django drf about many-to-many RelatedField custom field

I use the latest version of The Django REST Framework，
and The table in model is many-to-many related
My current model code looks like this:
model.py
class LvsDeploy(models.Model):
MASTER = 'MASTER'
BACKUP = 'BACKUP'
ROLE_CHOICES = (
(MASTER, 'MASTER'),
(BACKUP, 'BACKUP')
)
id = models.AutoField(primary_key=True)
cluster_name = models.CharField(max_length=30)
dip = models.CharField(max_length=15, verbose_name='DR IP')
role = models.CharField(max_length=10, choices=ROLE_CHOICES, verbose_name="role")
class LoadBalance(models.Model):
id = models.AutoField(primary_key=True)
lb_name = models.CharField(max_length=30, verbose_name='load balance')
cluster = models.ManyToManyField('LvsDeploy',related_name='cluster')
vip = models.CharField(max_length=50, verbose_name='VIP')
port = models.IntegerField(verbose_name='port')
def __str__(self):
return self.lb_name
My serializer code looks like this:
serializers.py
class LvsDeployReadOnly(serializers.ModelSerializer):
class Meta:
model = LvsDeploy
fields = '__all__'
class LoadBalanceSerializer(serializers.ModelSerializer):
cluster_name = serializers.RelatedField(source='cluster.name',read_only=True)
cluster = LvsDeployReadOnly(many=True)
##rs = RSInfoSerializer(many=True, read_only=True)
class Meta:
model = LoadBalance
fields = '__all__'
##extra_fields = ['rs','cluster','cluster_name']
extra_fields = ['rs','cluster','cluster_name']
My views code:
class BalanceList(views.APIView):
def get(self, request):
queryset = LoadBalance.objects.all()
serializer = LoadBalanceSerializer(queryset, many=True)
print(serializer.data)
return Response(serializer.data)
and request actual output:
[
{
"id": 2,
"cluster_name": null,
"cluster": [
{
"id": 1,
"cluster_name": "lvs_sz01",
"dip": "1.1.1.6",
"role": "BACKUP",
},
{
"id": 2,
"cluster_name": "lvs_sz01",
"dip": "1.1.1.5",
"role": "BACKUP",
}
],
"lb_name": "lb001",
"vip": "1.1.1.1",
"port": 80,
}
]
But the cluster_name filed value is same in the dictionary of lists .
I want the output to look like this：
[
{
"id": 2,
"cluster_name": "lvs_sz01",
"cluster": [
{
"dip": "1.1.1.6",
"role": "BACKUP",
},
{
"dip": "1.1.1.5",
"role": "BACKUP",
}
],
"lb_name": "lb001",
"vip": "1.1.1.1",
"port": 80,
}
]
How should I change it? Can you help me ?

I solved it myself with the following method：
class LoadBalanceSerializer(serializers.ModelSerializer):
cluster_name = serializers.SerializerMethodField()
cluster = LvsDeployReadOnly(many=True, read_only=True)
rs = RSInfoSerializer(many=True, read_only=True)
class Meta:
model = LoadBalance
fields = '__all__'
extra_fields = ['rs','cluster','cluster_name']
def get_cluster_name(self,obj):
print(type(obj.lb_name))
lvs_cluster = obj.cluster.all()
cluster_name = [ i.cluster_name for i in lvs_cluster ][0]
print(cluster_name)
return cluster_name
Thanks!

How to get parent model in child serializer without using depth?

I am new to django, i tried to practice django rest api implementation.
models.py
from django.db import models
class Parentmodel(models.Model):
ptid = models.IntegerField(primary_key=True)
ptname = models.CharField(default="",max_length=50)
def __str__(self):
return self.ptname
class Studentmodel(models.Model):
stid = models.IntegerField(primary_key=True)
stname = models.CharField(max_length=50)
ptid=models.ForeignKey(Parentmodel,db_column='ptid', related_name="student", on_delete=models.CASCADE)
def __str__(self):
return self.stname
class Marksmodel(models.Model):
Marksid=models.IntegerField(primary_key=True)
maths=models.IntegerField()
physics=models.IntegerField()
science=models.IntegerField()
stid=models.ForeignKey(Studentmodel,db_column='stid', related_name="marks", on_delete=models.CASCADE)
def __str__(self):
return self.Marksid
serializers.py
from rest_framework import serializers
from polls.models import Studentmodel, Marksmodel, Parentmodel
class MarksSerializer(serializers.ModelSerializer):
class Meta:
model=Marksmodel
fields="__all__"
class StudentSerializer(serializers.ModelSerializer):
marks=MarksSerializer(read_only=True,many=True)
class Meta:
model=Studentmodel
fields="__all__"
class ParentSerializer(serializers.ModelSerializer):
student=StudentSerializer(read_only=True,many=True)
class Meta:
model=Parentmodel
fields="__all__"
views.py
from rest_framework import viewsets
from .serializers import StudentSerializer, MarksSerializer, ParentSerializer
from .models import Studentmodel, Marksmodel, Parentmodel
class Studentapi(viewsets.ModelViewSet):
queryset = Studentmodel.objects.all()
serializer_class = StudentSerializer
class Marksapi(viewsets.ModelViewSet):
queryset = Marksmodel.objects.all()
serializer_class = MarksSerializer
class Parentapi(viewsets.ModelViewSet):
queryset = Parentmodel.objects.all()
serializer_class = ParentSerializer
Above code is working fine. I able to get the correct response if i call parent api.
Parentapi Response :
[
{
"ptid": 1,
"student": [
{
"stid": 1,
"marks": [
{
"Marksid": 1,
"maths": 100,
"physics": 100,
"science": 123,
"stid": 1
}
],
"stname": "Nainika",
"ptid": 1
}
],
"ptname": "Sabish"
}
]
Studentapi Response :
[
{
"stid": 1,
"marks": [
{
"Marksid": 1,
"maths": 100,
"physics": 100,
"science": 123,
"stid": 1
}
],
"stname": "Nainika",
"ptid": 1
}
]
My question is how to get the parent data in student api?

Django Rest Framework - Group data by its parent tag

Django Rest Framework - Group data by its parent tag
I have 3 serializers, One for tactics, one for techniques, one for sub techniques, and I'll be adding the sub techniques serializer as an explicit field to the techniques serializer.
models
class Tag(models.Model):
_id = models.CharField(max_length=10)
name = models.CharField(max_length=100)
def __str__(self):
return self._id
def __unicode__(self):
return self._id
class ModelA(models.Model):
_id = models.CharField(max_length=10)
title = models.CharField(max_length=100)
tags = models.ManyToManyField(Tag)
queries = ArrayField(models.TextField(),null=True, blank=True, default=list)
def __str__(self):
return self._id
def __unicode__(self):
return self._id
class ModelB(models.Model):
subtitle = models.ForeignKey(ModelA, on_delete=models.CASCADE)
def __str__(self):
return self.subtitle
serializers
# serializers
class TagSerializer(serializers.ModelSerializer):
def to_representation(self, value):
print(value)
return value.name
class Meta:
model = Tag
fields = ('name',)
class QueriesSerializer(serializers.ModelSerializer):
class Meta:
model = ModelB
fields = '__all__'
class ASerializer(serializers.ModelSerializer):
queries = QueriesSerializer(source='modelb_set', many=True)
tag = TagSerializer(many=True)
class Meta:
model = ModelA
fields = ('_id','title', 'tag','queries',)
class EndUserSerializer(serializers.ModelSerializer):
data = ??
class Meta:
model = ??
fields = '__all__'
I want to create a data visualization API where I need to use the results of ASerializer by their given tag in order to categorize each object into categories based on their associated tag if the object contains two tags, then it should be displayed in both . e.g
desired response
{
[
{
"tag": "Biologyl,
"data": [
{
"_id": str
"title": str
"tag": []
"queries": []
}
]
},
{
"tag": "Denoi2,
"data": [
{
"_id": str
"title": str
"tag": []
"queries": []
}
]
},
]
}
actual response
{
"_id": str
"title": str
"tag": []
"queries": []
}
viewset
#viewsets
class BooksViewSet(mixins.ListModelMixin,
viewsets.GenericViewSet):
queryset = ??.objects.all()
serializer_class = EndUserSerializer

You can use django-rest-multiple-models for receiving multiple querysets in the same view.
https://github.com/MattBroach/DjangoRestMultipleModels
It should look like this:
class BooksViewSet(ObjectMultipleModelAPIView):
querylist = [
{
'querylist': ModelA.objects.filter(tags__name="Biologyl"),
'serializer_class': EndUserSerializer,
'label': 'Biologyl',
},
{
'querylist': ModelA.objects.filter(tags__name="Denoi2"),
'serializer_class': EndUserSerializer,
'label': 'Denoi2',
},
....
]
You can also make it dynamic, but it seems a little bit dangerous👀.
class BooksViewSet(ObjectMultipleModelAPIView):
querylist = [
{
'querylist': ModelA.objects.filter(tags=tag),
'serializer_class': EndUserSerializer,
'label': tag.name,
}
for tag in Tag.objects.all()
]
See more https://django-rest-multiple-models.readthedocs.io/en/latest/object-options.html