Hi, you might take a look at this snippet: http://www.djangosnippets.org/snippets/950/
Basically it's a negative of what you want (i.e. w/o subclasses) but the idea I guess is there: you want a custom DB manager for which SuperClass.objects returns in fact the SubClass instances. I bet there are thousands of complications involving efficiency, filtering or multi-inheritance but with some simplifying assumptions I guess it's feasible. It looks like a fundamental ORM poroblem. I've made some research but haven't yet found a ready-to-go solution for it in Django. Please write how it went or maybe someone else already knows how to do it properly? Best regards, Mikołaj On Nov 28, 3:45 am, Rodrigo Cea <rodrigo...@gmail.com> wrote: > I have a parent Class "ComponentBase", with abstract=False, that many > other classes extend. > The parent Class has a ForeignKey relation to another class, "Band". > > It is convenient to be able to get a list of all of a band's > components without having to explicitly list each component class. > > I am doing this currently like so: > > class ComponentBase(models.Model): > band = models.ForeignKey(Band) > ... > class Meta: > abstract = False > > defsubclass(self): > try: return self.complogo > except: pass > try: return self.compnota > except: pass > try: return self.compalbumfotos > except: pass > ... > > where Complogo, Compnota, etc., are ComponentBase's sublclasses, like > so: > > class CompLogo(ComponentBase): > .... > > . With this, I can take an instance of Band and do: > > components = ComponentBase.objects.filter(band=band_instance) > > which populates "components" with all of the band's ComponentBase > instances, and then for each one callsubclass() to retrieve the > actual component, e.g. Complogo(). > > The thing is the number of components will likely increase in the > future, and it feels messy to keep extending the try/except list. Is > there a more compact and less verbose way of retrieving asubclass > instance when all you have is its parent class instance? -- You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to django-us...@googlegroups.com. To unsubscribe from this group, send email to django-users+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/django-users?hl=en.
