How can create Serializer with custom logic? - django-rest-framework

Question

Only two parameters come to the input:
param1 = Int, optional
param2 = Char, require
On output - json with 4 elements
key1 = Char
key2 = Int
key3 = Int
key4 = Int
Everything can be null
Now I have it implemented in the view in the get method, but I want to create a Serializer for this and put all the logic there, but I don’t really understand where to transfer the logic - validate, to_representation?
Now it looks something like this
views.py
class ExampleRetrieveApiView(APIView):
def get(self, request, *args, **kwargs):
# A lot of logic related with input parameters.
return Response({
'key1': value1,
'key2': value2,
'key3': value3,
'key4': value4
})
Need to do something like this
views.py
class ExampleRetrieveApiView(APIView):
serializer_class = ExampleSerializer
def get(self, request):
serializer = ExampleSerializer(???)
return Response(serializer.data)
serializers.py
class ExampleSerializer(serializers.Serializer):
???

Answer 1

Pass the input params as a dict. Then, you should use SerializerMethodField() for this:
from rest_framework import serializers
class ExampleSerializer(serializers.Serializer):
key1 = serializers.SerializerMethodField()
key2 = serializers.SerializerMethodField()
key3 = serializers.SerializerMethodField()
key4 = serializers.SerializerMethodField()
def get_key1(self, obj):
# do some calculations, let's say we want to return input1 multiplied by 2
# I'm accessing obj data and if it's empty assigning 0, you can add your own check instead
return obj.get('input1', 0)*2
def get_key2(self, obj):
# same deal, do whatever calculations you want with the input data
return obj.get('input2')
def get_key3(self, obj):
# your logic
return
def get_key4(self, obj):
return
For every field declared as SerializerMethodField, you should have a corresponding get_field method.
It's up to you how to get the input params, you can do it either through query params or body data.
Call the serializer like this in your view, for example with body params:
class ExampleRetrieveApiView(APIView):
def get(self, request):
input_data = {'input1':request.data.get('input1'),
'input2':request.data.get('input2')}
serializer = ExampleSerializer(input_data)
return Response(serializer.data)

Answer 2

views
class ExampleAPIView(APIView):
serializer_class = ExampleSerializer
def get(self, request):
serializer = ExampleSerializer(data=request.query_params)
if serializer.is_valid(raise_exception=True):
return(Response(serializer.data))
serializers
class ExampleSerializer(serializers.Serializer):
param1 = serializers.IntegerField()
param2 = serializers.CharField()
def validate(self, data):
#custom logic
data['param3'] = 'text'
#another params
return data
def to_representation(self, data):
return {
'key1': data['param3']
'key2': data['param4']
#another key for representation
}