python - Is it possible to filter "Related field" in Django Template?

Question

I am developing an Instagram clone using Django. I wanted to show the latest two comments for each post.

As of now, I am only able to show all comments using the below code

home.html

{% for comment in post.comments.all %}
   <p>{{ comment.user.username }}: {{ comment.description }}</p>
{% endfor %}

My models

class Comment(models.Model):

    user = models.ForeignKey(User, on_delete=models.CASCADE)
    post_linked = models.ForeignKey(Post, on_delete=models.CASCADE, related_name='comments')
    description = models.CharField(max_length=500)
    comment_posted_on = models.DateTimeField(default=timezone.now)

    def __str__(self):
        return "Comment by {} on {}".format(self.user.username, self.post_linked.caption)

Is there any way I cal display only the Latest two comment for each post?

question from:https://stackoverflow.com/questions/65905946/is-it-possible-to-filter-related-field-in-django-template

Answer 1

You should create the collection of filtered comments in your view, then include that in the template's context. Django's template philosophy is to make them as simple as possible which generally means no function calls (except for template tags and filters).

To make things a bit more efficient you should utilize prefetch_related and Prefetch. Checkout the docs on them for the best reference.

from django.db.models import Prefetch
posts = Post.objects.all().prefetch_related(
    Prefetch(
        'comments',
        Comment.objects.select_related('user').order_by('-comment_posted_on')[:2],
        to_attr='latest_comments',
    )
)

Then in your template:

{% for comment in post.latest_comments %}
   <p>{{ comment.user.username }}: {{ comment.description }}</p>
{% endfor %}