Hi Malcolm Many thanks for your verbose answer, i have to think the way i will represent this. By the moment i don't have instance variables over the state objects, so i was thinking that i could store the state "name" and make a getter using something like a Factory. How much awful seem to you this?
Many Many, Thanks Sebastian On 28 oct, 06:23, Malcolm Tredinnick <[EMAIL PROTECTED]> wrote: > On Sun, 2007-10-28 at 20:18 +1100, Malcolm Tredinnick wrote: > > On Sun, 2007-10-28 at 08:43 +0000, [EMAIL PROTECTED] wrote: > > > Hi Malcolm > > > In my design i have a class called publication, that behaves > > > different depending on the "state", so i have an state hierarchy that > > > implement via polymorphism the different ways the publication behaves. > > > I have been reading the djangobook and searching the net, looking a > > > way to implement this without lucky. Maybe i'm asking something a lot > > > trivial, sorry me if that is the case. > > > You can simulate inheritance by using foreign keys or one to one keys. > > For example: > > > class Parent(models.Model): > > some_data = ... > > .... > > > class Child(models.Model): > > parent = models.ForeignKey(parent, unique=True) > > ... > > I forgot to mention the alternative: storing complex object-oriented > hierarchies in SQL databases is officially a Hard Problem. It's just not > a natural fit for all cases. So turn your problem around a bit and don't > get stuck on one particular modelling method. Instead of storing the > classes directly like this, try to think of a way to flatten your > collection of classes. For example, if all of you "state nodes" can be > stored in a single model somehow, then you only need to store, in > addition to these models, the state transitions. > > Remember, state machines existed long before object-oriented > programming. There are other ways to represent the same information > without needing polymorphism and this might lead you to a more natural > representation. > > Regards, > Malcolm > > -- > The cost of feathers has risen; even down is > up!http://www.pointy-stick.com/blog/ --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Django users" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/django-users?hl=en -~----------~----~----~----~------~----~------~--~---
