So I have django model and I want to override save so that it only saves on certain instances. Is there a way to avoid a save from happening if a condition is met? The idea is if certain conditions defined with an if statement aren't met the instance fails to be saved. so for instance if there is not enough waiters we cancel the save, or if there is not enough tables we do the same.
Here's my code:
class Service(models.Model):
id = models.AutoField(primary_key=True)
arrival = models.DateTimeField(auto_now_add=True)
exit = models.DateTimeField(null=True, blank=True)
waiter = models.ForeignKey('Waiter', on_delete=models.CASCADE)
table = models.ForeignKey('Table', on_delete=models.CASCADE)
total_ammount= models.DecimalField(max_digits=15, decimal_places=2)
def save(self, *args, **kwargs):
if self.id == None:
time = datetime.datetime.now()
# check for waiters
waiters = Waiter.objects.select_related().annotate(num_Service=Count('service', filter=Q(service__exit__gt=time))).all()
available_waiters = waiters.filter(num_Service__lt=4)
avalable_waiters_length = len(available_waiters)
# check for tables
tables = Table.objects.select_related().annotate(num_Service=Count('service', filter=Q(service__exit__gt=time))).all()
available_tables = tables.filter(num_Service__lt=1)
avalable_tables_length = len(available_tables)
# return exception if a problem arises
if avalable_tables_length == 0 and avalable_waiters_length == 0:
print("not enough waiters or tables")
if avalable_waiters_length == 0:
print("not enough waiters")
return
if avalable_tables_length == 0:
print("not enough tables")
return
# assign waiter and table
waiter_obj = random.choice(available_waiters)
self.waiter = waiter_obj
table_obj = random.choice(available_tables)
self.table = table_obj
print(time.time())
# check if current time is open
if datetime.time(9,0) < time.time() and time.time()> datetime.time(21, 30):
print("The restaurant is closed")
return
print(time.time())
# add timedelta to init_time
if time.time() < datetime.time(17,0):
print(time + datetime.timedelta(minutes=90))
self.exit = time + datetime.timedelta(minutes=90)
if time.time() > datetime.time(17,0):
self.exit = time + datetime.timedelta(minutes=120)
#finalize pre_save
return super(Service, self).save(*args, **kwargs)
Thank you in advance :)
