[Zope-dev] ZPatterns: Non-ZODB storage and Racks

[Phillip J. Eby]

At 06:10 PM 11/8/00 +0200, Roch'e Compaan wrote:
>In Rack.py I noticed the following:
>
>        a = self.loadAttrib
>        if not a:
>            slot = self._writeableSlot(key)
>            slot[SelfKey] = item.aq_base    # strip acquisition wrapping
>            item._setSlot(slot)             # Not needed for non-ZODB
>storage
>
>If item._setSlot set is not needed for non-ZODB storage should I subclass
>rack and override createItem?
>

I'm not sure I understand your question.  If you don't have something
special you want to do by subclassing Rack, then the answer would be "no".  :)

The comment is perhaps misleading.  What it means is that the _setSlot call
isn't needed if your Rack implements a non-ZODB storage mechanism.  The
reason *why* it isn't needed, is that the DataSkin will ask for a slot on
demand, so that a ZODB record is only created if something needs to be
stored persistently.  However, in the case where you have not set a "load"
attribute (i.e., you are storing actual objects in the ZODB), then one
might as well tell the object its slot, because the slot is where the
object itself is going to be stored.  Technically, the _setSlot call isn't
necessary even then, because the DataSkin could still ask for it on demand.
 However, since the code at this point has gone to the trouble of getting
the slot object, it might as well pass it to the DataSkin immediately.