How do I exclude current object in ManyToMany query? - django

Question

I have two basic models, Story and Category:
class Category(models.Model):
title = models.CharField(max_length=50)
slug = models.SlugField()
...
class Story(models.Model):
headline = models.CharField(max_length=50)
slug = models.SlugField()
categories = models.ManyToManyField(Category)
...
And my view for story detail:
from django.views.generic import date_based, list_detail
from solo.apps.news.models import Story
def story_detail(request, slug, year, month, day):
"""
Displays story detail. If user is superuser, view will display
unpublished story detail for previewing purposes.
"""
stories = None
if request.user.is_superuser:
stories = Story.objects.all()
else:
stories = Story.objects.live()
return date_based.object_detail(
request,
year=year,
month=month,
day=day,
date_field='pub_date',
slug=slug,
queryset=stories,
template_object_name = 'story',
)
On the view for a given story object -- I'm using a generic detail view -- I'd like to display a list of stories related to the current story via the categories applied to the current story.
Here's how I'm doing this currently in the story detail template:
{% for category in story.category.all %}
<ul id="related_stories">
{% for story in category.story_set.all|slice:"5" %}
<li>{{ story.headline }}</li>
{% endfor %}
</ul>
{% endfor %}
This provides me what I need except I'd like to avoid displaying the linked headline for the story I'm viewing currently.
I believe this is done via the "exclude" filter, but I'm not sure if this belongs on the Category or Story model as a method, or how to construct it.
Any help would be appreciated!

Answer 1

Do this:
class Story(models.Model):
...
#property
def related_story_set(self):
category_id_list = self.category.values_list("id", flat=True)
return Story.objects.filter(category__id__in=category_id_list).exclude(id=self.id)
Then you can do this in the template:
<ul id="related_stories">
{% for related_story in story.related_story_set.all|slice:"5" %}
<li>{{ related_story.headline }}</li>
{% endfor %}
</ul>

Answer 2

You could just check in the template if the currently iterated story is the original story:
{% for category in story.category.all %}
<ul id="related_stories">
{% for substory in category.story_set.all|slice:"5" %}
{% if substory != story %}
<li>{{ story.headline }}</li>
{% endif %}
{% endfor %}
</ul>
{% endfor %}
You asked to put it in a model method:
class Story(models.Model):
...
def get_categories_with_stories(self):
categories = self.category.all()
for category in categories:
category.stories = category.story_set.exclude(id=self.id)[:5]
return categories
This doesn't solve your expensive query issue, but that wasn't a part of the question.
{% for category in story.get_categories_with_stories %}
<ul id="related_stories">
{% for substory in category.stories %}
<li>{{ story.headline }}</li>
{% endfor %}
</ul>
{% endfor %}