[Zope] Iterating descendants of base Z Class, how?

[Alexander Staubo]

Let's say I have a base Z Class "Project". Then I have a descendant Z
Class "WebProject". Is there a way to get a list of a folder's objects
that are project objects or descendants?

For example,

<!--#in "objectValues('Project')"-->
...

will only give me instances of the base class Project, _not_ any
WebProject instances. In order to do both, I have to do

<!--#in "objectValues('Project')"-->
...
<!--#/in-->
<!--#in "objectValues('WebProject')"-->
...
<!--#/in-->

But while this works, it's pretty inflexible, especially as I intend
invent new subclasses of Project, and I do not wish to rewrite this DTML
code every time I do.

I realize I can possibly enumerate the meta types through the Control
Panel, and then do objectValues() on each of the class names, but this
smells like a bitch job.

--
Alexander Staubo             http://www.mop.no/~alex/
"`Ford, you're turning into a penguin. Stop it.'"
--Douglas Adams, _The Hitchhiker's Guide to the Galaxy_