I have a ticket model, and its ticket serialiazer. The ticket model has a
*bought* and a *booked_at* field. And also a *unique_together* attribute
for *show* and *seat*.
class Ticket(models.Model):
show = models.ForeignKey(Show, on_delete=models.CASCADE)
seat = models.ForeignKey(Seat, on_delete=models.CASCADE)
user = models.ForeignKey(User, on_delete=models.CASCADE)
booked_at = models.DateTimeField(default=timezone.now)
bought = models.BooleanField(default=False)
class Meta:
unique_together = ('show', 'seat')
- On the ticket serializer, the serializer on validation checks whether
the ticket was bought or not.
- If it is bought, then it will raise an error.
- If its not bought then Check if the ticket was booked within 5
minutes.
- If its booked within 5 minutes, then raise an error.
- Else if the booked time is more than 5 minutes, than delete the
old ticket and return valid.
TicketSerializer:
class TicketSerializer(serializers.Serializer):
seat = serializers.PrimaryKeyRelatedField(queryset=Seat.objects.all())
show = serializers.PrimaryKeyRelatedField(queryset=Show.objects.all())
user = serializers.PrimaryKeyRelatedField(queryset=User.objects.all())
bought = serializers.BooleanField(default=False)
def validate(self, attrs):
if attrs['seat']:
try:
ticket = Ticket.objects.get(show=attrs['show'], seat=seat)
if not ticket.bought:
if ticket.booked_at < timezone.now() -
datetime.timedelta(minutes=5):
# ticket booked crossed the deadline
ticket.delete()
return attrs
else:
# ticket in 5 mins range
raise serializers.ValidationError("Ticket with same
show and seat exists.")
else:
raise serializers.ValidationError("Ticket with same
show and seat exists.")
except Ticket.DoesNotExist:
return attrs
else:
raise serializers.ValidationError("No seat value provided.")
On the view, I am using *@transaction.atomic()* to make sure the ticket/s
are created only if all of them are valid, or don't create ANY ticket if
not valid.
@transaction.atomic()
@list_route(
methods=['POST'],
)
def book_tickets_by_show(self, request, show_id=None):
try:
show = Show.objects.get(id=show_id)
user = request.user
...
...
data_list = [...]
with transaction.atomic():
try:
serializer = TicketSerializer(data=data_list, many=True)
if serializer.is_valid():
serializer.save()
....
return Response(serializer.errors,
status=status.HTTP_400_BAD_REQUEST)
except (Seat.DoesNotExist, ValueError, ConnectionError) as e:
return Response({'detail': str(e)},
status=status.HTTP_400_BAD_REQUEST)
except (Show.DoesNotExist, IntegrityError) as e:
return Response({'detail': str(e)},
status=status.HTTP_400_BAD_REQUEST)
What I would like to know is will it help in preventing when more than one
requests are called for creating the ticket/s for same seat/s?
Suppose, User A wants to book ticket with seat 5,6 and User B wants to book
ticket with seat 3,6, and another User C wants to book the ticket with
seats 2,3,4,5,6. Will the above method prevent booking tickets for their
respective seats for all the users, and only create tickets for one user
(maybe whose transaction was first)? Or if there is a better way then could
you please advice me how to. I hope I was clear. If not please ask.
Thank you
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