Hello there,
You should be able to achieve what you're after by using annotations[0].
In your case you'll want to declare your Event and Reservation relationship
explicitly by using
a ForeignKey
class Event(models.Model):
...
seating = models.PositiveIntegerField(default=0)
class Reservation(models.Model):
...
event = models.ForeignKey(Event, related_name='reservations')
seats = models.PositiveIntegerField(default=0)
And perform the following query
Event.objects.annotate(
seats_remaining=F('seating') - Sum('reservations__seats').
)
Cheers,
Simon
[0]
https://docs.djangoproject.com/en/2.1/topics/db/aggregation/#generating-aggregates-for-each-item-in-a-queryset
Le jeudi 6 septembre 2018 07:42:36 UTC-4, mab.mo...@gmail.com a écrit :
>
>
> QUESTION
>
> I have an application that will make on-line reservations for a series of
> weekly events. I would like to display the list of upcoming events in an
> html template with the number of remaining seats available in a single html
> page. I was able to create views to display the list of upcoming events and
> another view to display the number of remaining seats available but I am
> unable to figure out how to nest the two into a single view. Example
> below...
>
> HTML OUTPUT
>
> Event Title Week 1 - x amount of seats remaining for this event
>
> Event Title Week 2 - x amount of seats remainign for this event
>
> Event Title Week 3 - x amount of seats remaining for this event
>
> and so on ....
>
> MODELS
>
> class Events(models.Model):
> event_date = models.DateField(auto_now_add=False)
> event_time = models.TimeField(auto_now_add=False)
> event_type = models.CharField(max_length=20, choices=EVENT_TYPE)
> seating = models.IntegerField(default=0)
> title = models.CharField(max_length=200)
> description = models.TextField()
> menu = models.TextField()
> price = models.DecimalField(max_digits=6, decimal_places=2)
> publish = models.CharField(max_length=1, choices=PUBLISH_CHOICE)
>
> def __int__(self):
> return self.title
>
> class Reservations(models.Model):
> user_id = models.IntegerField(default=0)
> event_id = models.IntegerField(default=0)
> reservations = models.IntegerField(default=0)
>
> def __int__(self):
> return self.event
>
>
> VIEWS
>
> def events_view(request):
>
> events=Events.objects.filter(publish='Y').filter(event_date__gte=datetime.now()).order_by('event_date')
>
> reservation_count = Reservations.objects.aggregate(Sum('reservations'))
>
> return render(request, 'restaurant/events.html',{"events":events,
> "reservation_count":reservation_count, })
>
> def make_reservation_view(request, pk):
> event = Events.objects.get(id=pk)
> seating_available = Events.objects.get(id=pk)
> seating_available = seating_available.seating
> reservation_count =
> Reservations.objects.filter(event_id=pk).aggregate(res_sum=Sum('reservations'))
> res = reservation_count['res_sum']
> seats_remaining = seating_available - res
>
> return render(request, 'restaurant/make_reservation.html',
> {"event":event, \
>
> "seats_remaining":seats_remaining,})
>
>
>
--
You received this message because you are subscribed to the Google Groups
"Django users" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to django-users+unsubscr...@googlegroups.com.
To post to this group, send email to django-users@googlegroups.com.
Visit this group at https://groups.google.com/group/django-users.
To view this discussion on the web visit
https://groups.google.com/d/msgid/django-users/4a2f159c-af8a-4d1d-932d-13bbe40cd1c7%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
