Django serializers: What does is_valid actually do?

Question

git repo: django tutorial

I've been following the above django project that looks at creating at person to person chat. I've come across this part:

def message_list(request, sender=None, receiver=None):
    ...

    elif request.method == 'POST':
        print('posting')
        data = JSONParser().parse(request)
        print(data)
        serializer = MessageSerializer(data=data)
        print(serializer)
        if serializer.is_valid():
            serializer.save()
            return JsonResponse(serializer.data, status=201)

class MessageSerializer(serializers.ModelSerializer):
    sender = serializers.SlugRelatedField(many=False, slug_field='email', queryset=User.objects.all())
    receiver = serializers.SlugRelatedField(many=False, slug_field='email', queryset=User.objects.all())

    class Meta:
        model = Message
        fields = ['sender', 'receiver', 'message', 'timestamp']

What does "if serializer.is_valid():" actually do? Is it checking that the data in the message matches the data in the user profile? I've never used serializers before and could use an explanation of it.

Thanks

Answer 1

You need to call is_valid during deserialization process before write data to DB. is_valid perform validation of input data and confirm that this data contain all required fields and all fields have correct types. If validation process succeded is_valid set validated_data dictionary which is used for creation or updating data in DB. Otherwise serializer's property errors will contain information about errors in input data, and you can send this information as HTTP response in your view.