Calling a foreign key relationship in an “if” statement in Django template

Question

I have two models, Booking and Confirmation that are related via a ForeignKey relationship through "booking." I want to only display bookings in my detail view that have an attribute value of is_confirmed ==True. I don't really want a queryset, I just want to display the booking information from the "Booking" model if the confirmation is True in the template.

models.py:

class Booking(models.Model):
    user = models.ForeignKey(CustomUser, null=True, default='', on_delete=models.CASCADE)
    expert = models.ForeignKey(CustomUser, null=True, default='',on_delete=models.CASCADE, related_name='bookings')
    title = models.CharField(max_length=200, default='Video call with ..', null=True)
    start_time = models.DateTimeField('Start time', null=True)
    end_time = models.DateTimeField('End time', null=True)
    notes = models.TextField('Notes', blank=True, null=True) 

    class Meta:
        verbose_name = 'Booking'
        verbose_name_plural = 'Bookings'

    def get_absolute_url(self):
        return reverse('booking:booking_detail', kwargs={"pk": self.pk})

class Confirmation(models.Model):
    booking = models.ForeignKey(Booking, on_delete=models.CASCADE)
    expert_confirming = models.ForeignKey(CustomUser, on_delete=models.CASCADE)
    is_confirmed = models.BooleanField(default=False)

    def get_absolute_url(self):
        return reverse('booking:booking_detail', kwargs={"pk": self.booking_id})

views.py:

class BookingDetailView(DetailView):
    model = Booking
    template = 'templates/booking_detail.html'

booking_detail.html:

<div class="container" id="booking_content">
    <p>{{ booking.title }}</p>
    <p>{{ booking.start_time }}</p>
    <p>Booking request by: {{ booking.user }}</p>
    <p>Expert requested: {{ booking.expert }}</p></div>

I'm not sure how the if statement in the template should reference these related models to display what I want.

Answer 1

I think that with the way you have your models you would have to run a query on the Confirmation model to determine whether there exists a confirmation for a particular booking. But why have a separate confirmation model at all? Try just moving the relevant field into the booking model:

class Booking(models.Model):
    user = models.ForeignKey(CustomUser, null=True, default='', on_delete=models.CASCADE)
    expert = models.ForeignKey(CustomUser, null=True, default='',on_delete=models.CASCADE, related_name='bookings')
    title = models.CharField(max_length=200, default='Video call with ..', null=True)
    start_time = models.DateTimeField('Start time', null=True)
    end_time = models.DateTimeField('End time', null=True)
    notes = models.TextField('Notes', blank=True, null=True)
    is_confirmed = models.BooleanField(default=False) # just this field since you already have an expert.

That simplifies things, and puts a little less load on your db. Then, you can show only bookings that are confirmed with this template language:

{% if booking.is_confirmed %}

    <div class="container" id="booking_content">
        <p>{{ booking.title }}</p>
        <p>{{ booking.start_time }}</p>
        <p>Booking request by: {{ booking.user }}</p>
        <p>Expert requested: {{ booking.expert }}</p>
    </div>

{% else %}
    ...
{% endif %}

You may have a good reason for having a separate confirmation model. If so, then this answer is irrelevant. If not, then maybe this could help simplify things for you.