[Zope] conceptual problem with acquisition

[Rik Hoekstra]

Oliver Frommel wrote:
> 
> Hello,
> 
> although I already created some sites with Zope I now encountered a problem
> that I am not able to solve with acquisition, i.e. to make a parent subfolder
> work as a fallback resource. Directories look like this:
> 
> /pics/logo.gif
> /dir/subdir1/pics/logo.gif
> /dir/subdir1/index_html (subdir1 is a zclass and index_html a method of it)
> /dir/subdir2/pics/logo.gif
> /dir/subdir2/index_html (subdir2 is a zclass and index_html a method of it)
> /dir/subdir3/pics/   (empty!)
> /dir/subdir3/index_html (subdir3 is a zclass and index_html a method of it)
> 
> The index_html contains a reference to the pic: <img src="pics/logo.gif">
> Now when the subdirX/pics/ doesn't not contain a logo.gif, acquisition also
> does not work because it stops on finding the pics folder in the subdirX.
> This is exactly the scenario, Rik Hoekstra describes in
> http://www.zope.org/Members/Hoekstra/ChangingZopeContexts.
> 
> Unfortunately non of the workarounds he mentions are appropriate because
> a) I need an image folder for each subdir (see below)
> b) I can't reference images from the parent
> c) the pic directories need to have the same name
> 
> this all because the rationale behind this is to enable index_html to look
> differently _dependent_ on the existence of logo.gif.
> the site designers are meant to be able to change index_html's appearance
> just by uploading a new logo.gif. If this is not present, the one of the
> parent should be used.
> 
> I think it would work if I put the images directly in subdirX and in the
> root dir but this is pretty ugly and should only serve as a last ressort IMHO.
> 
> is there any way / product / trick to make this concept work with subdirs??

an explicit PythonScript (or DTML Method) should do the trick:

include a PythonScript in your zclass (or somewhere else) with the following
code (name: findlogo; standard bindings):

try: 
    getattr(context.pics, 'logo') # if logo is the name of the picture
    logo = context.pics.logo      
except AttributeError:
    logo = context.<fallbackdirectory>.pics.logo # in which fallback directory
is your rootdir

return logo


instead of the <img srcs="pics.logo.gif"), make your index_html refer to
<dtml-var findlogo>

this should do the trick. I tested it on a very simple setup, where it worked.
Let me know if this helps.

hth

Rik