Mixin and inheritance example

views.py

class OrderStatus(object):
    
    NEW = 'new'
    PAID = 'paid'
    DELIVERED = 'delivered'
    CANCELLED = 'cancelled'

    COMPLETED_STATES = (
        DELIVERED,
        CANCELLED,
    )

class ReadOnlyViewSet(
        mixins.RetrieveModelMixin,
        mixins.ListModelMixin,
        viewsets.GenericViewSet):
    """Common base view for readonly views, similar is provided by DRF.""""

    pass


class PermissionsMixin(object):
    """"
    This mixin assumes that model has a company attribute that should 
    match the user.

    """

    def get_queryset(self):
        queryset = (
            super(PermissionsMixin, self)
            .get_queryset())
        if self.request.user.is_superuser():
            # admin
            # extra query, aggregation?
            pass
        else:
            # regular user
            queryset = queryset.filter(company=self.request.user.company)
        return queryset


class OrderView(PermissionsMixin, ReadOnlyViewSet):
    """"Common view for order readonly views."""

    queryset = Order.objects.all()


class CompletedOrderView(OrderView):
    """This filter does not rely on request."""

    queryset = Order.objects.filter(
        order_status__in=OrderStatus.COMPLETED_STATES
    )


class RecentOrdersView(OrderView):
    """This filter does rely on time of request."""

    def get_queryset(self):
        return (
            super(RecentOrderView, self)
            .get_queryset()
            .filter(created__gt=now() - datetime.timedelta(hours=2))
        )