how can i order items based on a method - django

Question

i wanna know how can i order a listView using a method , like here i wanna order my posts based on numbers of likes , i am using class based views ... here is my code
models.py
class Post(models.Model):
author = models.ForeignKey(User, on_delete=models.CASCADE)
title = models.CharField(max_length=200)
# content = models.TextField()
content = RichTextField(blank=True, null=True)
date_created = models.DateTimeField(auto_now_add=True)
post_image = models.ImageField(upload_to='post/cover')
category = models.CharField(choices=LABEL_CHOICES, max_length=1)
slug = models.SlugField()
likes = models.ManyToManyField(User, related_name='blogpost_like')
def __str__(self):
return self.title
def get_absolute_url(self):
return reverse("core:detail", kwargs={
'slug': self.slug
})
def delete(self, *args, **kwargs):
self.post_image.delete()
super().delete(*args, **kwargs)
#property
def comment_numbers(self):
return Comment.objects.filter(post=self).count()
def number_of_likes(self):
return self.likes.count()
views.py
class PostListView(ListView):
model = Post
template_name = 'home.html'
context_object_name = 'posts'
paginate_by = 6
ordering = ['-date_created']

Answer 1

You cannot use a function to do that but you can write a query to do it. You would need to override get_queryset first of all then use the aggregation function Count:
from django.db.models import Count
class PostListView(ListView):
model = Post
template_name = 'home.html'
context_object_name = 'posts'
paginate_by = 6
def get_queryset(self):
queryset = super().get_queryset()
queryset = queryset.annotate(
number_of_likes=Count('likes')
).order_by('number_of_likes')
return queryset