[Zope3-dev] IGroupFolder instead of isinstance?

[Roger Ineichen]

Is there a reason why we don't use a IGroupFolder interface?

I see some problems for future implementations like described
in the groupfolder.txt in zope.app.authentication.browser

----
[...] groups need to be defined in it's group folder. 
Other groups folders or group-defining plugins could 
define groups for a group.
----

because:

In the class zope.app.authentication.groupfolder.py

There is a check against a instance instead asking for 
providing a interface?

for name, groupfolder in groupfolders:
        # It's annoying that we have to filter here, but there isn't
        # a good reason for people to register group folder utilities.
        if not isinstance(groupfolder, GroupFolder):
               ^^^^^^^^^^
            continue
        principal.groups.extend(
            groupfolder.getGroupsForPrincipal(principal.id),
            )

or are events more private and we have to implement own
events for custom implementations? This looks like the event
was added specialy for one implementation.

Regards
Roger Ineichen
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