[Zope] Indirection, acquisition, asphyxiation

[Steve Alexander]

Dennis Nichols wrote:

> I'm having trouble using the value of a property to determine which
> object to render (Zope 2.2.1, if it makes any difference). Starting from
> the beginning, let's say I have two folders A and B with four DTML
> methods (Nilo, Alpha, Smalpha, and Bravo):
> 
> /
>    Nilo
>    /A
>       Alpha
>       Smalpha
>    /B
>       Bravo
> 
> From Alpha, I can render Nilo, Smalpha, and Bravo by using this dtml:
> 
>   <dtml-var Nilo>       (or <dtml-var "Nilo">)
>   <dtml-var Smalpha>    (or <dtml-var "Smalpha">)
>   <dtml-var "B.Bravo">  (not <dtml-var B.Bravo>!)
> 
> OK, now I want a property of folder A, call it 'choice', to determine
> what should be rendered by Alpha. So I rewrite Alpha to include:
> 
>   either <dtml-var "_[choice]">
>       or <dtml-var "_.getitem(choice)">
> 
> These work nicely if I set 'choice' to 'Nilo' or 'Smalpha' but I don't
> see how to make either one work for Bravo! Setting 'choice' to 'B.Bravo'
> gives me:
> 
> Error Type: KeyError
> Error Value: B.Bravo
> 
> How do I get this to work for Bravo (and still keep it working for the
> other cases)? Clearly my zen needs some tending to.

You can use restrictedTraverse('slash/delimited/path')

If you have a slash at the start, the traversal starts from the Zope 
root object. Otherwise, it is relative.

You can also use a sequence to represent your path. The slash at the 
start is represented by an empty string at the beginning of your sequence.

See the documentation on the interfaces Wiki.

http://www.zope.org/Members/michel/Projects/Interfaces/Traversal

Also, see lib/python/OFS/Traversable.py

--
Steve Alexander
Software Engineer
Cat-Box limited
http://www.cat-box.net