Return just the last object in Django REST Framework

Question

I'm new to asking on StackOverflow and to Django so I'm sorry if I made any mistakes.

So far, I have a basic API with Django and REST Framework. I want to return just the last object that was added to the database, which could be done with the highest ID.

This is the models.py:

from django.db import models

class Humidity(models.Model):
    value = models.FloatField()

class Temperature(models.Model):
    value = models.FloatField()
    isFarenheit = models.BooleanField()

I don't have any time fields, but I can add them if necessary.

This is the serializers.py:

class HumiditySerializer(serializers.ModelSerializer):
    class Meta:
        model = Humidity
        fields = ('id', 'value')

class TemperatureSerializer(serializers.ModelSerializer):
    class Meta:
        model = Temperature
        fields = ('id', 'value', 'isFarenheit')

And this is the views.py:

from django.shortcuts import render
from rest_framework import viewsets, permissions
from .models import Humidity, Temperature
from .serializers import HumiditySerializer, TemperatureSerializer

class HumidityView(viewsets.ModelViewSet):
    queryset = Humidity.objects.order_by('-id')[0]
    serializer_class = HumiditySerializer

class TemperatureView(viewsets.ModelViewSet):
    queryset = Temperature.objects.order_by('-id')[0]
    serializer_class = TemperatureSerializer

This is the traceback of the error:

Traceback (most recent call last):
  File "C:\Users\usuario\AppData\Local\Programs\Python\Python37-32\lib\threading.py", line 917, in _bootstrap_inner
    self.run()
  File "C:\Users\usuario\AppData\Local\Programs\Python\Python37-32\lib\threading.py", line 865, in run
    self._target(*self._args, **self._kwargs)
  File "C:\Users\usuario\AppData\Local\Programs\Python\Python37-32\lib\site-packages\django\utils\autoreload.py", line 54, in wrapper
    fn(*args, **kwargs)
  File "C:\Users\usuario\AppData\Local\Programs\Python\Python37-32\lib\site-packages\django\core\management\commands\runserver.py", line 117, in inner_run
    self.check(display_num_errors=True)
  File "C:\Users\usuario\AppData\Local\Programs\Python\Python37-32\lib\site-packages\django\core\management\base.py", line 390, in check
    include_deployment_checks=include_deployment_checks,
  File "C:\Users\usuario\AppData\Local\Programs\Python\Python37-32\lib\site-packages\django\core\management\base.py", line 377, in _run_checks
    return checks.run_checks(**kwargs)
  File "C:\Users\usuario\AppData\Local\Programs\Python\Python37-32\lib\site-packages\django\core\checks\registry.py", line 72, in run_checks
    new_errors = check(app_configs=app_configs)
  File "C:\Users\usuario\AppData\Local\Programs\Python\Python37-32\lib\site-packages\django\core\checks\urls.py", line 13, in check_url_config
    return check_resolver(resolver)
  File "C:\Users\usuario\AppData\Local\Programs\Python\Python37-32\lib\site-packages\django\core\checks\urls.py", line 23, in check_resolver
    return check_method()
  File "C:\Users\usuario\AppData\Local\Programs\Python\Python37-32\lib\site-packages\django\urls\resolvers.py", line 398, in check
    for pattern in self.url_patterns:
  File "C:\Users\usuario\AppData\Local\Programs\Python\Python37-32\lib\site-packages\django\utils\functional.py", line 80, in __get__
    res = instance.__dict__[self.name] = self.func(instance)
  File "C:\Users\usuario\AppData\Local\Programs\Python\Python37-32\lib\site-packages\django\urls\resolvers.py", line 579, in url_patterns
    patterns = getattr(self.urlconf_module, "urlpatterns", self.urlconf_module)
  File "C:\Users\usuario\AppData\Local\Programs\Python\Python37-32\lib\site-packages\django\utils\functional.py", line 80, in __get__
    res = instance.__dict__[self.name] = self.func(instance)
  File "C:\Users\usuario\AppData\Local\Programs\Python\Python37-32\lib\site-packages\django\urls\resolvers.py", line 572, in urlconf_module
    return import_module(self.urlconf_name)
  File "C:\Users\usuario\AppData\Local\Programs\Python\Python37-32\lib\importlib\__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1006, in _gcd_import
  File "<frozen importlib._bootstrap>", line 983, in _find_and_load
  File "<frozen importlib._bootstrap>", line 967, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 677, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 728, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "C:\Users\usuario\Desktop\Subcarpetas\iot-sensors\iot-sensors-backend\iot-sensors-backend\iotSensors\iotSensors\urls.py", line 21, in <module>
    path('', include('api.urls')),
  File "C:\Users\usuario\AppData\Local\Programs\Python\Python37-32\lib\site-packages\django\urls\conf.py", line 34, in include
    urlconf_module = import_module(urlconf_module)
  File "C:\Users\usuario\AppData\Local\Programs\Python\Python37-32\lib\importlib\__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1006, in _gcd_import
  File "<frozen importlib._bootstrap>", line 983, in _find_and_load
  File "<frozen importlib._bootstrap>", line 967, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 677, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 728, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "C:\Users\usuario\Desktop\Subcarpetas\iot-sensors\iot-sensors-backend\iot-sensors-backend\iotSensors\api\urls.py", line 6, in <module>
    router.register('humidity', views.HumidityView)
  File "C:\Users\usuario\AppData\Local\Programs\Python\Python37-32\lib\site-packages\rest_framework\routers.py", line 75, in register
    basename = self.get_default_basename(viewset)
  File "C:\Users\usuario\AppData\Local\Programs\Python\Python37-32\lib\site-packages\rest_framework\routers.py", line 162, in get_default_basename
    return queryset.model._meta.object_name.lower()
AttributeError: 'Humidity' object has no attribute 'model'

This error is only thrown when I change in the views.py from Humidity.objects.all() to Humidity.objects.order_by('-id')[0] and the same with temperature.

How do I return the last object saved?

Answer 1

Since you don't have time or date fields in your model, you may retrieve the latest object only through id.

Humidity.objects.all().order_by('-id')[:1]

-id retrieves the objects in the reverse order. Since QueryDict object of django is lazily loaded, this will only retrieve the latest value.

You can use the last function to retrieve the latest object

Humidity.objects.all().latest()

or just retrieve the object with the latest id by

Humidity.objects.latest('id')