Hello I started with Django couple weeks ago, I wanted to return the objects that are closest to the location send in the query parameters. I think that the function get_querryset is never called because it doesn't change anything. These are the files I have:

#models.py
from django.contrib.gis.db import models

class CarOffering(models.Model):
    name = models.CharField(max_length=200)
    location = models.PointField(null=True,blank=True)

    def __str__(self):
        return self.name

#serializer.py
from .models import CarOffering
from rest_framework import serializers

class CarSerializer(serializers.ModelSerializer):
    distance = serializers.FloatField(source='distance.mi', read_only=True, required=False)
    class Meta:
        model = CarOffering
        fields = ['name','location', 'distance']
        read_only_fields = ['location']

#Views.py
from .models import CarOffering
from django.contrib.gis.geos import GEOSGeometry
from django.contrib.gis.db.models.functions import Distance
from .serializers import CarOfferingSerializer

from django.shortcuts import render
from rest_framework.generics import ListCreateAPIView

import geocoder

class ListCreateCarOffering(ListCreateAPIView):
    queryset = CarOffering.objects.all()
    serializer_class = CarOfferingSerializer

    def get_querryset(self):
        qs = super().get_querryset()
        latitude = self.request.query_params.get('lat', None)
        longitude = self.request.query_params.get('lng', None)

        if latitude and longitude:
            pnt = GEOSGeometry('POINT('   str(longitude)   ' '   str(latitude)   ')', srid=4326)
            qs = qs.annotated(distance=Distance('location', pnt)).order_by('distance')

        return qs

#urls.py
from django.contrib import admin
from django.urls import path
from proj.views import ListCreateCarOffering

urlpatterns = [
    path('admin/', admin.site.urls),
    path('api/caroffer', ListCreateCarOffering.as_view(),name = 'list_caroffer')

When I look in http://127.0.0.1:8000/api/caroffer I get the same thing as if I do http://127.0.0.1:8000/api/caroffer?lat=0&lng=0:

[
    {
        "name": "test2",
        "location": "SRID=4326;POINT (-0.9024781294996892 37.71827450265065)"
    },
    {
        "name": "test3",
        "location": "SRID=4326;POINT (0 0)"
    }
]

Any idea why I don't get the distance attribute? Thank you!

CodePudding user response：

I'm somewhat new to Django as well, but was able to get this working by defining the "get" method under the ListAPIView, and then working with the queryset & response params from there.

I didn't go through the trouble of installing the dependencies for the Distance expression; nonetheless, the URL dispatch still seemed to run the desired annotate method:

class ListCreateCarOffering(ListCreateAPIView):
    queryset = CarOffering.objects.all()
    serializer_class = CarSerializer

    def get(self, request):
        
        latitude = self.request.query_params.get('lat', None)
        longitude = self.request.query_params.get('lng', None)

        if latitude and longitude:

            pnt = "id"
            qs = self.queryset.annotate(distance=Count(pnt)).order_by('distance')

        return HttpResponse([{'name': q.name, 'location': q.location, 'distance': q.distance} for q in qs])