django - Querying model field data in template/views without get_object_or_404()

Question

Homefeed is the page where i query all the blogposts

In this project, any user that sees a blogpost that they are interest in can submit their interest to the post. 1 user can only submit 1 interest to that blogpost, but they can submit as many interest as they want to different blogposts.

Right now in my home.html, I am trying to make it such that if YOU have submitted interest,(aka your interest status is at pending or accept or decline) for that particular blog post, you will see the view interest button instead of the submit interest button.

But I am facing a problem because in my views, I am querying for blog_posts = BlogPost.objects.all() and not blog_post = get_object_or_404(BlogPost, slug=slug). As such, how am I able to query whether or not for the particular blogpost, the user has already submitted an interest in my template to determine which button should show in my home.html? Thanks, and also I dont want to change the url at all :)

views.py

def home_feed_view(request, *args, **kwargs):
    context = {}
    blog_posts = BlogPost.objects.all()
    context['blog_posts'] = blog_posts 
    page = pageFilter(request.GET, queryset=BlogPost.objects.exclude(author_id=request.user.id).order_by('date_updated')) 
    context['page'] = page
    paginated_page = Paginator(page.qs, 4)
    page = request.GET.get('page')
    page_obj = paginated_page.get_page(page)

    context['page_obj'] = page_obj
    return render(request, "HomeFeed/snippets/home.html", context)

home.html

{% for post in page_obj %}

{% if post.interest_set.exists and request.user.is_authenticated %}

     <a class="btn btn-info btn-sm" href="{% url 'HomeFeed:submitinterest' post.slug %}">View Interest</a>
     {% else %}  
      <a class="btn btn-warning btn-sm" href="{% url 'HomeFeed:submitinterest' post.slug %}">Submit Interest</a>
      {% endif %}
      {% endfor %}

urls.py

path('', home_feed_view , name= "main"),

models.py

class Account(AbstractBaseUser):
 email                  = models.EmailField(verbose_name="email", max_length=60, unique=True)
 username               = models.CharField(max_length=30, unique=True)

class BlogPost(models.Model):
 title                  = models.CharField(max_length=50, null=False, blank=False, unique=True)
 author                     = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
 slug                   = models.SlugField(blank=True, unique=True)

class Interest(models.Model):
   user = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
   blog_post = models.ForeignKey(BlogPost, on_delete=models.CASCADE)

class InterestInvite(models.Model):

   ACCEPT = "ACCEPT"
   DECLINE = "DECLINE"
   PENDING = "PENDING"
   STATUS_CHOICES = [
      (ACCEPT, "accept"),
      (DECLINE, "decline"),
      (PENDING, "pending"),

   ]

   interest = models.OneToOneField(Interest, on_delete=models.CASCADE, related_name="interest_invite")   
   status = models.CharField(max_length=25, choices=STATUS_CHOICES, default=PENDING)
   objects= models.Manager

views.py

        type = TypeFilter(request.GET, queryset=BlogPost.objects.exclude((Q(author_id__in=request.user.blocked_users.all()) | Q(author = request.user))).order_by('date_updated')).annotate(user_has_interest=Case(When(interest__user=request.user, then=Value(True)), default=False, output_field=BooleanField()))

Using Django filters: filters.py

class TypeofIdeaFilter(django_filters.FilterSet):
    title = django_filters.CharFilter(field_name="title", lookup_expr='icontains')

    class Meta:
        model = BlogPost

question from:https://stackoverflow.com/questions/65914725/querying-model-field-data-in-template-views-without-get-object-or-404

Answer 1

You can annotate a field on your query:

from django.db.models import Case, When, Value, BooleanField

blog_posts = BlogPost.objects.all().annotate(
    user_has_interest=Case(When(interest__user=request.user, then=Value(True)), default=False, output_field=BooleanField())
)

Now you can check in your template using if-else:

{% if post.user_has_interest %}
    Something
{% else %}
    Something else
{% endif %}