Untitled

class EventEdit(UpdateView):
    model = Event
    form_class = EventForm
    template_name = 'event-add-edit.html'
    success_url = reverse_lazy('event-list')

    @login_required
    def dispatch(self, request, *args, **kwargs):
        params = {
            'event': self.get_object(),
            'member': request.member,
            'editor': True,
        }
        can_edit = EventParticipant.objects.filter(**params).exists()
        if not can_edit:
            messages.error(request, 'Not authorized')
            next = reverse('event-view', kwargs={'id': event.id})
            return redirect(next)
        return super(EventEdit, self).dispatch(request, *args, **kwargs)