Django display related count - django

Question

i currently try to display who many posts a category has.
Therefor i created the Post Model and the Category Model (See below):
models.py
# Categorys of Post Model
class Category(models.Model):
title = models.CharField(max_length=255, verbose_name="Title")
class Meta:
verbose_name = "Category"
verbose_name_plural = "Categories"
ordering = ['title']
def __str__(self):
return self.title
#Post Model
class Post(models.Model):
author = models.ForeignKey('auth.User', on_delete=models.CASCADE)
title = models.CharField(max_length=200)
text = models.TextField(max_length=10000)
category = models.ForeignKey(Category, verbose_name="Category", on_delete=models.CASCADE, null=True)
tag = models.CharField(max_length=50, blank=True)
postattachment = fields.FileField(upload_to='postattachment/%Y/%m/%d/', blank=True, null=True)
postcover = fields.ImageField(upload_to='postcover/%Y/%m/%d/', blank=True, null=True, dependencies=[
FileDependency(processor=ImageProcessor(
format='JPEG', scale={'max_width': 300, 'max_height': 300}))
])
created_date = models.DateTimeField(default=timezone.now)
published_date = models.DateTimeField(blank=True, null=True)
def publish(self):
self.published_date = timezone.now()
self.save()
def __str__(self):
return self.title
category_list.html
{% extends 'quickblog/base.html' %}
{% block content %}
{% for categories in categories %}
<div>
<h1><u>{{ categories.title }} {{ $NumCountGetHere }}</u></h1>
</div>
{% endfor %}
{% endblock %}
Now i have no idea how to get the related objects counted...?

Answer 1

You can use something like this:
{% for cat in categories %}
<div>
<h1><u>{{ cat.title }} {{ cat.post_set.count }}</u></h1>
</div>
{% endfor %}
The model Post has a Foreignkey field to the model Category. You can access the related Post instances from a given Category instance using the manager category_instance.post_set. Read about it in the docs.
Finally, we use the method .count() on this manager to get the number of related posts for that given category. This way the code ends up looking like {{ cat.post_set.count }}.