Re: How models.Manager is working behind the scene and calling different serialize methods?

Ohk, I got it now..

Thanks for clarifying this.

My further doubts in continuation of this are.

1. For confirmation, ModelName.objects.all() calls get_queryset() method, while ModelName.objects.get calls get() method internally.

2. In above code to override default serialize method of BasicUserUpdate for get_queryset() method,

We have to do 2 things.

1. Inherit default models.Manager and override get_queryset() method.

2. Inherit  models.QuerySet and override default serialize method.

Honestly it seems overkill for this problem.
Can u please suggest alternative straight forward way to do it in model only.

On Friday, May 29, 2020 at 3:34:39 PM UTC+5:30, Sencer Hamarat wrote:

I believe, the method "get_queryset" name is explains what you want to know.

If you filter or fetch every thing with django query, it returns queryset.

The .get() query on the other hand, returns a single object.

Saygılarımla,

Sencer HAMARAT

On Fri, May 29, 2020 at 4:43 AM django-newbie <arjit...@gmail.com> wrote:

Hi,

I am new to django and going through a tutorial and now confused with one particular implementation.

models.py

import json
from django.core.serializers import serialize

from django.db import models
from django.conf import settings

# Create your models here.


def upload_update_image(instance, filename):
    return "updates/{owner}/{filename}".format(owner=instance.owner, filename=filename)

class UpdateQuerySet(models.QuerySet):
 
    def serialize(self):
        print("UpdateQuerySet serialize")
        print(self.values("owner", "content", "image"))
        list_values = list(self.values("owner", "content", "image"))
        return json.dumps(list_values)


class UpdateManager(models.Manager):

    def get_queryset(self):
        print('get_queryset method')
        return UpdateQuerySet(self.model, using=self._db)


class BasicUserUpdate(models.Model):
    owner = models.ForeignKey(settings.AUTH_USER_MODEL,on_delete=models.CASCADE)
    content = models.TextField(blank=True,null=True)
    image = models.ImageField(blank=True,null=True,upload_to=upload_update_image,)
    updated = models.DateTimeField(auto_now=True)
    timestamp = models.DateTimeField(auto_now_add=True)

    def __str__(self):
        return self.content or ''

    objects = UpdateManager()


    def serialize(self):
        print("BasicUserUpdate serialize")
        try:
            image = self.image.url
        except:
            image = ""
        data = {
            "content": self.content,
            "owner": self.owner.id,
            "image": image
        }
        data = json.dumps(data)
        return data

 

views.py

from basic.models import BasicUserUpdate
from django.views import View
from django.http import HttpResponse


class BasicUserUpdateListView(View):
    def get(self, request, *args, **kwargs):
        qs = BasicUserUpdate.objects.all()
        json_data = qs.serialize()
        return HttpResponse(json_data, content_type='application/json')

class BasicUserUpdateDetailView(View):

    def get(self, request,id, *args, **kwargs):
        qs = BasicUserUpdate.objects.get(id=id)
        json_data = qs.serialize()
        return HttpResponse(json_data, content_type='application/json')

]

At run time calling ListView, get below print messages
get_queryset method
UpdateQuerySet serialize

At run time calling DetailView, get below print messages
get_queryset method
BasicUserUpdate serialize

How Django is identifying which serialize method to be called?

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