RE: [Zope] Zope 2.5 and TransparentFolder incompatibility

11 Jun 2002

      All I'm saying is there are other ways to cope, since I don't think TF can
be 'fixed.'

Eventually, I think it is likely that I will write a product that will do
something to allow "views" of folder to be a native characteristic of the UI
for the product, but I don't currently have time.

Creating your own product and subclassing folder should pose no real issues,
since the main thing you would be hacking would be just the UI (all the core
functionality of ObjectManager derived classes would still be there via
inheritance).  You would add an extra DTML method on the filesystem within
your product to provide a limited view of the folder, using some crieteria
to filter (I don't think underscore is doable, so you will have to come up
with another filter scheme, by substing in id, or meta_type, or something
else).  Some example code (not guaranteed to work, but a place to start) is
below.  It assumes that you subclass folder, and create a few methods to
filter results of ObjectManager API calls, and use these filtered results in
DTML replacing manage_main for your custom folder.

Good Luck, and I hope this makes some sense.
Sean

###############################

import Globals
from OFS import Folder, SimpleItem, ObjectManager, PropertyManager
from Globals import Persistent, Acquisition
import AccessControl

class CustomFilteredFolder(Folder):
	"""Custom Folder with Enhanced UI"""

	__ac_permissions__=(
        	('View management screens', ('manage_main',
'manage_viewall')),
        	('View', ('index_html')),
        	)

	manage_allcontents = Folder.manage_main #standard manage_main is now
going to be another tab
	manage_main        = Globals.HTMLFile('dtml/filteredContents',
globals()) #file dtml/filteredContents.dtml

	#ZMI Tabs, customized: code copied from OFS.Folder and modified
      manage_options=(
	  ({'label':'Filtered Contents', 'action':'manage_main'},
	   {'label':'All Contents', 'action':'manage_allcontents'},
         {'label':'View', 'action':'index_html',
         'help':('OFSP','Folder_View.stx')},
        )+
        PropertyManager.PropertyManager.manage_options+
        AccessControl.Role.RoleManager.manage_options+
        SimpleItem.Item.manage_options+
        FindSupport.FindSupport.manage_options
        )

	meta_type="Filtered View Folder"

	def __init__(self, id):
		"""Initialize CustomFilteredFolder Instance"""
		Folder.__init__(self, id)
		self.hiddenObjectsIdPattern  = ('sql')
		#assumption would be that if the string 'sql' appeared
within 
		#the id, that it would be hidden/filtered

		self.hiddenObjectsMetaTypes  = ('Z SQL Method')
		#or, this could be done with a meta_type

	def objectItemsFiltered(self):
		"""Filter results of OM.objectItems"""
		#unimplemented do something here
	def objectIdsFiltered(self):
		"""Filter results of OM.objectIds"""
		#unimplemented do something here
	def objectValuesFiltered(self):
		"""Filter results of OM.objectValues"""
		#unimplemented do something here

	### Note: DTML for the filtered views would use objectItemsFiltered,
where
	### normally, it would use objectItems() instead (i.e.
manage_allcontents
	### would still use OM methods.

-----Original Message-----
From: Howard Hansen [mailto:zope@halfmagic.com]
Sent: Monday, June 10, 2002 4:59 PM
To: sean.upton@uniontrib.com; dirk.datzert@rasselstein-hoesch.de
Cc: zope@zope.org; ct@gocept.com
Subject: Re: [Zope] Zope 2.5 and TransparentFolder incompatibility

Thanks for the response Sean, but could we try this again?  This is not the
answer I want to hear.  Could you start your message with something like:
"I've patched TF so it will work perfectly with 2.5 and all subsequent
versions...." ;-)

Seriously, this is not the first time I've heard the "TransparentFolders
Considered Harmful" argument, and at some level I'm inclined to agree.  Just
not at the level of someone who has to wade through tons of dinky objects in
his ZMI, nor at the level of someone who has to change lots of his code to
account for other changes.

It's too bad we can't use an underscore at the beginning of an object's id.
Then we could have a "Hidden Contents" tab in the ZMI and view them that
way.  This would give us one transparent folder in each folder.  A boy can
dream.

This leads me to a different question: how safe (or stable) is it to
subclass folder and add some new behaviors to it?  People blithely talk
about doing it all the time, but my Zope sites total between 2000 and 5000
hits an hour.  I get concerned about maintaining stability and performance.
Obviously bad coding = bad performance and/or instability, but assuming
competent coding, can I expect my subclassed folder to work as well as
Folder?

Howard Hansen
http://howardsmusings.com/categories/zope

----- Original Message -----
From: <sean.upton@uniontrib.com>
To: <zope@halfmagic.com>; <dirk.datzert@rasselstein-hoesch.de>
Cc: <zope@zope.org>; <ct@gocept.com>
Sent: Monday, June 10, 2002 3:34 PM
Subject: RE: [Zope] Zope 2.5 and TransparentFolder incompatibility
...
TFs are bad bad bad... too much magic to the namespace stack.  They break
Core Session Tracking in Zope < 2.5, and likely don't work with sessions
in
Zope 2.5.  The reason for this is that with the session id manager (which
in
CST has to have the same name every time), you cannot have more than one
(because TF screws up the namespace stack globally, and makes the session
id
managers appear to already exist for a folder that they don't, or
something
like that, I can't remember exactly)...  If you really want the benefits
of
TF without the headache and unpredictability, your best bet if you want to
hide/sort objects in a folder is to create your own product, subclass
folder, and hack the dtml files in the product for the UI to only show
what
you want (perhaps putting everything else into another ZMI tab or
something?).
Sean

RE: [Zope] Zope 2.5 and TransparentFolder incompatibility

sean.upton＠uniontrib.com