Related name returning post.commentpost.none - django

Question

Can anyone explain me, why i get Post.CommentPost.None?
How to correct connect CommentPost with Posty in query? I need get {{posty.comments.user}} my result is Post.CommentPost.None
Here something about my models and functions.
class Posty(models.Model):
title = models.CharField(max_length=250, blank=False, null=False, unique=True)
sub_title = models.SlugField(max_length=250, blank=False, null=False, unique=True)
content = models.TextField(max_length=250, blank=False, null=False)
image = models.ImageField(default="avatar.png",upload_to="images", validators=[FileExtensionValidator(['png','jpg','jpeg'])])
author = models.ForeignKey(Profil, on_delete=models.CASCADE)
updated = models.DateTimeField(auto_now=True)
published = models.DateTimeField(auto_now_add=True)
T_or_F = models.BooleanField(default=False)
likes = models.ManyToManyField(Profil, related_name='liked')
unlikes = models.ManyToManyField(Profil, related_name='unlikes')
created_tags = models.ForeignKey('Tags', blank=True, null=True, related_name='tagi', on_delete=models.CASCADE)
test_wyswietlenia = models.IntegerField(default=0, null=True, blank=True)
class CommentPost(models.Model):
user = models.ForeignKey(Profil, on_delete=models.CASCADE)
post = models.ForeignKey(Posty, on_delete=models.CASCADE, related_name="comments")
content1 = models.TextField(max_length=250, blank=False, null=False)
date_posted = models.DateTimeField(default=timezone.now)
date_updated = models.DateTimeField(auto_now=True)
VIEWS
tag = request.GET.get('tag')
if tag == None:
my_tag = Posty.objects.prefetch_related('comments')
my_view = Posty.objects.prefetch_related('my_wyswietlenia')
else:
my_tag = Posty.objects.filter(created_tags__tag=tag)
my_view = Posty.objects.prefetch_related('my_wyswietlenia')
TEMPLATES
{% for post in my_tag %}
{% if post.comments.last.user == None %}
<span class="forum_tag_author">Komentarz » Brak komentarza</span><br/>
<span class="forum_tag_author">Stworzony przez » {{post.author}} </span><hr/>
{% else %}
<span class="forum_tag_author">Komentarz » {{post.comments.last.content1}}</span><br/>
<span class="forum_tag_author">Odpowiadający » Dodany przez: {{post.comments.last.user}} </span><hr/>
{% endif %}
{% endfor %}
And this
{{post.comments}} give a request Post.CommentPost.None
What is problem? What i do bad?

Answer 1

You can use a Subquery expression [Django-doc] to obtain the latest content1 comment and author with:
from django.db.models import OuterRef, Subquery
last_comment = CommentPost.objects.filter(post=OuterRef('pk')).order_by('-date_posted')
my_tag = Posty.objects.annotate(
last_comment=Subquery(last_comment.values('content1')[:1]),
last_comment_user=Subquery(last_comment.values('user__name')[:1]),
last_comment_user_pk=Subquery(last_comment.values('user')[:1])
).prefetch_related('my_wyswietlenia')
The __name might be different, since it depends on the fields of you Profil model.
Then you can render the content and the last author with:
{% for post in my_tag %}
{{ post.last_comment }} by {{ post.last_coment_user }}
{% enfor %}