Class hierarchy problem

[Jordi Riera]

Are you using a db for that?

Django models would handle that pretty easily:

class Species(models.Model):
     name = models.CharField()

class Genus(models.Model):
    name = models.CharField()
    species = models.ManyToManyField(
         Species, related_name = 'genus_species'
    )

then you can access species from genus by:
Genus.objects.all()[0].species.all()

and genus from species by:
Species.objects.all()[0].genus_species.all()

if you can afford this depends that would solve your issue I think.
more details:
http://stackoverflow.com/questions/9352662/how-to-use-the-reverse-of-a-django-manytomany-relationship

Regards
Jordi


On Tue, Aug 6, 2013 at 5:36 PM, BrJohan <brjohan at gmail.com> wrote:

> On 06/08/2013 16:02, Chris Angelico wrote:
>
>  My classhierarchy is like a multilevel tree where each non-leaf node
>>> (class)
>>> is given knowledge about its nearest subclasses and their 'capacities'.
>>>
>>> So, my idea is to let the 'upper' class recursively choose which of its
>>> nearest subclasses is the 'correct' one, until approaching a 'leaf' class
>>> from which the instance should be created. And, given my knowledge that a
>>> solution along the lines of this idea has been designed and was working,
>>> I'm
>>> still hopeful ... (or I'll have to investigate all those old backup-DVDs)
>>>
>>
>> [ responding on-list - I hope it was mere oversight that had this come
>> privately to me alone ]
>>
>> This is code smell; this recursive search for the "right" class seems
>> likely to be wrong. Can you have the classes perhaps register
>> themselves in some way? On what basis is a superclass to determine
>> that one of its subclasses should handle this request?
>>
>> ChrisA
>>
>>
>
> Consider a botanical classification system (somewhat analogous to my
> 'problem' as it effectively is related to classification of entities):
>
> A Domain should know about its Kingdoms,
> a Kingdom should know about its Phylums,
> ...
> a Genus should know about its Species.
>
> Of course it is possible to implement such a decision tree as a 'factory'.
> However, I would rather prefer to encapsulate those decisions at the class
> level where they 'belong'.
>
> BrJohan
> --
> http://mail.python.org/**mailman/listinfo/python-list<http://mail.python.org/mailman/listinfo/python-list>
>



-- 
- Jordi Riera, Connecting people.
+33 662217507
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