From: Brian Candler <B.Candler@...>
Date: 2007-04-19T04:18:46+09:00
Subject: Re: Recursive method not working

On Thu, Apr 19, 2007 at 01:05:05AM +0900, Zouplaz wrote:
> Hi, I'm trying to display a hierarchical tree but there's something 
> wrong with the method below.
> The result var is 'lost' between the calls - I mean, each "#{result}" 
> contains the right value at the end of the method (I checked that), but 
> that value is lost when returning to the upper level.
> 
> I don't see why...
> 
> Thanks for your help !
> 
 1> def affiche_arbre(rubriques)
 2>     for rubrique in rubriques
 3>       result = '<br/>'
 4>       0.step(rubrique.level) { result += '&nbsp;'}
 5>       result += rubrique.libelle + ' ' + link_to('+', :action => 'new', :parent_id => rubrique) + ' '
 6>       unless rubrique.parent_id == nil
 7>         result += link_to('E', :action => 'edit', :id => rubrique) + ' ' + link_to('D', :action => 'delete', :id => rubrique )
 8>       end
 9>       if rubrique.children.size > 0
10>         result += affiche_arbre(rubrique.children)
11>       end
12>     end
13>     "#{result}"
14> end

Well, the only recursive call I can see is line 10. You append the return
values from these calls onto 'result'. But then in line 12 you go back
around the loop, and in line 3 you reinitialise result, thereby throwing
away everything you've calculated so far.