Django Detailed View: Retrieving data from another model in a detailed view

Question

I am trying to show a list of associated "cliqueclasses" to a given "Item", but am just not able to get the template for the loop right. I'd also like to take this one step further and attach only the classes associated to the item (based on the foreign key)

I have been trying for a while and haven't had any luck so far particularly with the template!

Models.py

class Item(models.Model):
    title = models.CharField(max_length=100)
    price = models.FloatField()
    discount_price = models.FloatField(blank=True, null=True)
    category = models.CharField(choices=CATEGORY_CHOICES, max_length=2)
    label = models.CharField(choices=LABEL_CHOICES, max_length=1)
    slug = models.SlugField()
    description = models.TextField()
    image = models.ImageField()

    def save(self, *args, **kwargs):
    ...

    def __str__(self):
        return self.title
    ...

class CliqueClass(models.Model):
    title = models.CharField(max_length=100)
    start_date = models.DateTimeField(auto_now_add=True)
    end_date = models.DateTimeField(auto_now_add=True)
    item = models.ForeignKey(Item, related_name='items',
                             on_delete=models.CASCADE)
    description = models.TextField()
    plan = models.TextField()
    slug = models.SlugField()
    image = models.ImageField()

    def save(self, *args, **kwargs):
    ...

    def __str__(self):
    ...

My Views.py

class ItemDetailView(DetailView):
    model = Item
    template_name = "clique.html"
    # queryset = CliqueClass.objects.filter(title=Item.title)

    def get_context_data(self, **kwargs):
        """
        This has been overridden to add `cliqueclass` to the template context,
        now you can use {{ cliqueclass }} within the template
        """
        context = super().get_context_data(**kwargs)
        context['cliqueclass'] = CliqueClass.objects.all()
        return context

My URL's.py

path('clique/<slug>/', ItemDetailView.as_view(), name='clique'),

My clique.html template:

 {% for class in object.cliqueclass_set.all %}
  <!--Look through all cliques classes-->
  <div class="mb-3">
    <a href="">
      <span>{{ class }}</span>
      <span class="badge purple mr-1">{{ class.title }}</span>

      <p>Lorem ipsum dolor sit amet consectetur adipisicing elit. Natus suscipit modi sapiente illo soluta odit
        voluptates,
        quibusdam officia. Neque quibusdam quas a quis porro? Molestias illo neque eum in laborum.</p>

    </a>
  </div>

  <hr class="solid">
  {% endfor %}

Any help would be really appreciated :)

didn't the `{% for class in object.cliqueclass_set.all %}` loop work for you? — JPG, Aug 18 '20 at 04:05
@ArakkalAbu unfortunately not, the HTML page is loading and I am able to call attributes of the Item model on the template - but can't seem to enter the for loop of the clique class — Danie, Aug 18 '20 at 04:12
What do you see when you execute the following statement, `print(context['object'].cliqueclass_set.all().count())` just top of the `return context`? — JPG, Aug 18 '20 at 04:17
@ArakkalAbu An error came up: _print(context['object'].cliqueclass_set.all().count()) AttributeError: 'Item' object has no attribute 'cliqueclass_set' [18/Aug/2020 14:20:11] "GET /clique/danie-camp/ HTTP/1.1" 500 94884_ — Danie, Aug 18 '20 at 04:22
Bingo...thats why it is not rendering in the template. The template will simply ignore the execution if it encounters any error during the process — JPG, Aug 18 '20 at 04:23
Brilliant thank you @ArakkalAbu - thanks for walking me through the debug process lol! this did the job: print(context['cliqueclass'].all().count())_ You're a legend :) — Danie, Aug 18 '20 at 04:31

score 1 · Accepted Answer · answered Aug 18 '20 at 04:32

First, you need to change the related_name of the FK

class CliqueClass(models.Model):
    # rest of your code
    item = models.ForeignKey(Item, related_name='clique_classes',
                             on_delete=models.CASCADE)

related_name can be any arbitrary name, But, I think clique_classes is the more suitable name.

If you're not familiar with the related_name, read more

After changing the related_name, you need to migrate the database by executing the following commands,

python manage.py makemigrations
python manage.py migrate

Then, in your view, remove the get_context_data(...) method, as it is not relevant to this particular issue.

class ItemDetailView(DetailView):
    model = Item
    template_name = "clique.html"

Then, change the template code to

{% for clique_class in object.clique_classes.all %}
    {{ clique_class.title }}
{% endfor %}

Django Detailed View: Retrieving data from another model in a detailed view

1 Answers1