On Friday 19 August 2005 04:03 pm, computing project wrote:
> Hi,
>
> I'd like to change the way that the catalog is implemented slightly, to
> allow tools other than the workflow tool to provide variables to the
> catalog.  I'm happy to submit the code + tests if everyone's
> happy/interested.
>
> 1.  Provide a new interface.  Currently, only the workflow tool implements
> this interface
>
> class ICatalogVariableProvider(Interface):
>
>   def getCatalogVariablesFor(obj):
>      """Return a dictionary of additional properties to be made available
> to the catalog when an object is indexed
>      """
>      return vars
>
> 2.  Change the catalog tool to something like:
>
>       def catalog_object(self, obj, uid, idxs=None, update_metadata=1):
>         vars = {}
>         for tool in self._providers:
>            pt = getToolByName(obj, tool, None)
>            if pt:
>               vars.update( pt.getCatalogVariablesFor( obj ) )
>
>         w = IndexableObjectWrapper(vars, obj)
>         ZCatalog.catalog_object(self, w, uid, idxs, update_metadata)
>
>       where at the moment, _providers would be just a one-item tuple (
> 'portal_workflow', )
>
> This way it's much easier to hook other tools in at indexing time by adding
> them to the list, rather than needing to create a new catalog class.  (note
> this code is a rough cut-and-paste, so it might well have typos - for
> illustration only!)
>
> Any thoughts?  Is this useful?

In Plone 2.1 we have an ExtensibleIndexableObjectWrapper which allows products 
to register methods with the catalog for use in indexing and metadata.  I 
think this handles the same (or similar) usecases in a different but 
potentially more flexible manner.  Plone uses it to register all sorts of 
tool methods, rather than indexing python scripts or something similarly 
inefficient.  Hopefully this might make it into the CMF core at some point.

Alec Mitchell
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