#96: Extensible index object wrapper
- Contents
We have been adding stuff like getObjSize and getObjPositionInParent to ATCT because we want it to be cataloged efficiently. These things don't feel like they really belong there though. How about extending our IndexableObjectWrapper class (see CatalogTool.py) to add those attributes for cataloging only? That's how allowedRolesAndUsers works.
- Proposed by
- Stefan Holek
- Seconded by
- Christian 'Tiran' Heimes
- Proposal type
- Architecture
- Repository branch
- plip96-extensibleindexobjectwrapper
- State
- completed
Definitions
registry -- a place to register something
wrapper -- a design pattern to add behavior to an object by wrapping it transparently
global -- non persistent and zope wide var
local -- persistent and placeful var
Motivation
There is no need to add api methods to content types or slow ttw scripts with an extensible index object wrapper.
Also see summary
Proposal
Replace the current IndexableObjectWrapper with an ExtensibleIndexObjectWrapper + a register that contains a mapping between attribute name and a callable.
The ExtensibleIndexObjectWrapper return the indexed object's attribute when the attribute name isn't listed in the registry. If the name is in the registry then the registered callable is called with the object as argument and the value is returned.
IMO there is no need to have a local (per site) registry at the moment so we should follow the sacret rules of KISS and YAGNI and stick to a simple global dict like registry.
Maybe use a registry of adapters
maintained product in order to work correctly, and I've been looking
for a good general solution like this. I was glad to find this
PLIP on file.
I wonder whether it might be more natural to implement this as a
registry of Five/Z3 adapters. Adapters are called in exactly
this way, as a bare function with the object as argument, but
a single adapter can apply a bundle of related methods to
an object.
Another idea that could be pulled in from Z3 is the use of
interfaces to invoke the registered adapter selectively
on objects undergoing (re)indexing. This would make me very
happy because it would completely cover my own use case
(!). But it would also be generally handy to be able to
discriminate between content types in this way.
If there is any way I can help out with this, let me know!