Django model advice for chained ForeignKeys approach - django

Question

I have these models in Django 1.5
class Number(models.Model):
number = models.CharField("Patient's Number", max_length=12, unique=True)
class Appointment(models.Model):
to_number = models.ForeignKey(Number)
message = models.CharField("Message", max_length=160)
I would like the Appointment model to hold another field that will allow me to add how many times the user wants to be notified via email before the actual appointment time (similar to how we add multiple popup/email notifications in Google calendar). Since I'm still a newbie in web development, Django and database models, I have a hard time deciding how to create and link up models to achieve this. One solution that I thought of is to create another model and link it up with Appointment like this:
class Notification(models.Model):
appointment = models.ForeignKey(Appointment)
time = models.TimeField("Time before appointment we must notify the user")
Is that even a sensible approach? If not, what should I do instead? Also, in order to see both Appointment and Notification in Number's view via admin console, what should I declare the Inline stacks (since now that Number --> Apppointment --> Notification, what is the right way to link those up as Inline when viewed under Number's page)? I know something like [this has been asked before] (Nested inlines in the Django admin?), but since it's been asked in 2010, I'm curious as to if anyone has found a new way to do it or if the second answer by #carruthd in the aforementioned link is still the best way to go about it. Thank you.

Answer 1

If you want more notifications for each appointment, add ManyToManyField pointing to another model (Notification in this case). Then you're able to get all upcoming Notifications in this way:
Appointment.notifications_set.filter(notify_time__gte=now()).
class Notification(models.Model):
notify_time = models.DateTimeField("Notification datetime", db_index=True)
class Number(models.Model):
number = models.CharField("Patient's Number", max_length=12, unique=True)
class Appointment(models.Model):
to_number = models.ForeignKey(Number)
message = models.CharField("Message", max_length=160)
notifications = models.ManyToManyField(Notification, through=AppointmentNotifications)
class AppointmentNotifications(models.Model):
notif = models.ForeignKey(Notification)
appoint = models.ForeignKey(Appointment)
There's one more table: AppointmentNotifications, which would be created by Django anyway, but if you create it by yourself, you're able to add some columns later (ie. notification_already_sent = models.BooleanField("User was informed") and you also probably want to display all Notifications joined to each Appointment as an inline:
admin.py:
class AppointmentNotificationInline(admin.TabularInline):
model = AppointmentNotification
class AppointmentAdmin(admin.ModelAdmin):
inlines = [AppointmentNotificationInline]