Re: none

[David Philippi]

On Wednesday 14 August 2002 17:26, Ingo Ruhnke wrote:
> Factories must not jump around in the XML tree, they should work on
> the node they get and fail if it is an empty one. Since the above kind
> cause quite funny and hard to track down errors, like this one:
> AxisFactory::create(cur);
> AxisFactory::create(cur->next);

Taking a look into the code I've found the reason why the factories check for 
empty nodes. While I still consider a create(cur->next) ugly, I do call them 
using create(cur->children) after I've found the start of the section.
As long as we don't want to enforce a very strict syntax in the config file 
it's quite possible that a factory will be called with an empty node first 
this way (as far as I understand libxml).
In order to change this, I'd have do step down into cur->children itself to 
check for empty nodes and then call the factory.
I dislike this for two reasons:
1) the controller shouldn't be interested in what's inside a <scroller> tag
2) I don't know how to get back to the parent using clean code

I won't write code like

if ( ! strcmp(reinterpret_cast<const char*>(cur->name), "scroller"))
  {
   cur=cur->children;
    while (xmlIsBlankNode(cur))
       cur = cur->next;

    scroller = ScrollerFactory::create(cur);

    cur=cur->parent; // does this exist?
  }

only to avoid a xmlIsBlankNode inside the factory. In my opinion a factory 
should be able to deal with a
<scroller>



   <some-scroller>
</scroller>

itself. It's not that it really does jump around in the tree, it's starting 
point is the node below <scroller> and it won't ever touch anything above.

Bye David