Re: [Zope-dev] re: Subclassing ZObjectManager in ZClasses

[Dieter Maurer]

Daniel Rogahn writes:
 > 
 > >Summary: (when creating a folderish ZClass and cascading base classes) if
 > >ZObjectManager isn't subclassed at 1st level, objects can be added to the
 > >folderish ZClass instances but they don't show in the manage_main object
 > list.
I can explain, why it happens. I think it is a bug, at least a mis-feature.
But I cannot change it :-(

  "OFS.SimpleItem.Item" provides stupid (!) implementations
  of "objectItems", "objectIds" and "objectValues"
  (all return the empty tuple).

  I do not know, why in hell a non-ObjectManager implements
  ObjectManager methods. Because it does, you get the
  behaviour you complain about.

  "OFS.SimpleItem.Item" is essentially what is called
  "ZObject" in ZClasses and what you get when
  the "Include standard Zope object behavior" is checked.

  When your class (deriving von ZObject) comes before
  "ZObjectManager", then its stupid "objectItems"
  method is inherited and not that of "ZObjectManager".
  This changes, when you switch the inheritance order.

The solution:

  "OFS.SimpleItem.Item" should not define ObjectManager methods.

  Unfortunately, many "dtml-tree" applications will probably break then.
  Affected will be "dtml-tree" occurences with "branches=objectValues".


Dieter

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[Zope-dev] re: Subclassing ZObjectManager in ZClasses

[Daniel Rogahn]

re: http://lists.zope.org/pipermail/zope-dev/2000-March/004034.html
This message is about 1.5 years old, but no replies?, & I haven't seen any
similar messages or howtos?

--Alexandre Ratti  Fri, 31 Mar 2000
>Summary: (when creating a folderish ZClass and cascading base classes) if
>ZObjectManager isn't subclassed at 1st level, objects can be added to the
>folderish ZClass instances but they don't show in the manage_main object
list.

>Here I first created MyBaseClass, then I subclassed it together with
>ZObjectManager when creating MyTestClass
...
>when I add objects in an instance of MyTestClass they do not show
>in the object list (Content view). I *think* they are actually added
>because I cannot add an additional one with the same ID: I get an "ID
>already in use" error.

>It's not that bad, but I can't create a standard base class, then use it to
>create a folderish variant.

I have the same symptoms, objects dont display in a folder subclass, but are
there.
Heres how I fixed it:

Your base class must be the last in the class inheritance list.  You must
add all other base classes first.  This will almost always be a problem
because most base classes start with ZClass... and will be last
alphabetically.  (this will be much easier to fix if/when you can change, or
at least reorder, the base classes of an object)
eg: ZObject, ZObjectManager, CatalogAwareBase, MyBaseClass

If you have a complicated object, I think you can export it in XML, reorder
the base classes, & reimport.  But adding/removing classes this way doesn't
update the management interface tabs.

Daniel Rogahn
[EMAIL PROTECTED]
http://www.d.umn.edu/~drogahn/


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