django restful filtering by derived field - django

Question

I was wondering if I can use a serializer to add two columns of a database, package it, and as a bonus FILTER by it.
models.py
class Snippet(models.Model):
time1= models.DateTimeField()
time2 = models.DateTimeField()
serializers.py
class SnippetSerializer(serializers.ModelSerializer):
sometime= UnixEpochDateField(source = 'time1') # special serializer that converts a datetime to epoch (below)
sometime2= UnixEpochDateField(source = 'time2') # special serializer that converts a datetime to epoch (below)
sometime_SUM = sometime + sometime2 # THIS DOES NOT WORK!
class Meta:
model = Snippet
fields = ('sometime_SUM')
class UnixEpochDateField(serializers.DateTimeField):
def to_native(self, value):
""" Return epoch time for a datetime object or ``None``"""
import time
try:
return calendar.timegm(value.utctimetuple())
except (AttributeError, TypeError):
return None
def from_native(self, value):
import datetime
try:
value = float(value)
except:
raise serializers.ValidationError("Not a number. Input: %s %s"%(type(value), value))
if value < 0:
raise serializers.ValidationError("Cannot be less than 0. Input: %s"%value)
return datetime.datetime.utcfromtimestamp(float(value))
views.py
class SnippetList(APIView):
"""
List all snippets, or create a new snippet.
"""
filter = ('sometime_SUM') # THIS DOES NOT WORK!
def get(self, request, format='json'):
snippets = Snippet.objects.all()
filter = SnippetFilter(request.GET, queryset = snippets) # THIS DOES NOT WORK!
serializer = SnippetSerializer(filter, many=True)
return Response(serializer.data)
I have highlighted the code that doesn't work that I naively thought would work.
The url command I want to use is /someurl/snippets/?sometime_SUM>4
EDIT:
Apparently, I can't filter by a serialize field. So let me modify my question to, can I filter by time1, except when I input the time from my website to the API, i am using EPOCH time, instead of the time1, DATETIME
Thanks #mariodev