Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.python > #52051

Re: Class hierarchy problem

Show all headers | View raw

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

Back to comp.lang.python | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Class hierarchy problem BrJohan <brjohan@gmail.com> - 2013-08-06 11:10 +0200
  Re: Class hierarchy problem Chris Angelico <rosuav@gmail.com> - 2013-08-06 10:30 +0100
    Re: Class hierarchy problem Chris Angelico <rosuav@gmail.com> - 2013-08-06 15:02 +0100
      Re: Class hierarchy problem BrJohan <brjohan@gmail.com> - 2013-08-06 17:36 +0200
        Re: Class hierarchy problem Joe Junior <joe.fbs.junior@gmail.com> - 2013-08-06 13:23 -0300
        Re: Class hierarchy problem Jordi Riera <kender.jr@gmail.com> - 2013-08-06 18:13 +0200
        Re: Class hierarchy problem Chris Angelico <rosuav@gmail.com> - 2013-08-06 18:12 +0100
        Re: Class hierarchy problem Terry Reedy <tjreedy@udel.edu> - 2013-08-06 19:13 -0400
        Re: Class hierarchy problem Ben Finney <ben+python@benfinney.id.au> - 2013-08-07 11:58 +1000
  Re: Class hierarchy problem Peter Otten <__peter__@web.de> - 2013-08-06 11:34 +0200
  Re: Class hierarchy problem Steven D'Aprano <steve@pearwood.info> - 2013-08-06 09:36 +0000
  pexpect,  loading an entry field inq1ltd <inq1ltd@inqvista.com> - 2013-08-06 11:05 -0400
  Re: pexpect, loading an entry field "Lakshmipathi.G" <lakshmipathi.g@gmail.com> - 2013-08-06 22:04 +0530
  Re: pexpect, loading an entry field inq1ltd <inq1ltd@inqvista.com> - 2013-08-06 14:03 -0400
  Re: pexpect, loading an entry field "Lakshmipathi.G" <lakshmipathi.g@gmail.com> - 2013-08-07 13:40 +0530

csiph-web