[Zope-dev] More useful CatalogAware class?

[Martijn Pieters]

On Mon, Jun 12, 2000 at 01:12:33PM -0700, Michel Pelletier wrote:
> Amos and I and the guys at Activestate were discussing cataloging at a
> recent training sessions and we came up with the following possible
> successor to CatalogAware.
> 
> The idea is that a CatalogAware object looks for two methods that return
> sequecnes of Catalogs that many be interested in this object.  The first is
> class defined method 'getClassCatalogs', the second is an instance defined
> method 'getLocationCatalogs' that the instance can get from its classes, its
> instance dict, or acquisition.
> 
> The idea is that you provide methods that define the policy for finding
> Catalogs.  The default class defined 'getClassCatalogs' is identical
> behavior to the old CatalogAware, but you can and probably will override it.

Very interesting indeed.

Is the CatalogAware mixin in the future going to move towards Tres' Observable
pattern?

After initial notification of the set of catalogs (or other interested
objects, or a generic notification manager) at creation time, the object will
only have to call the 'notify' method, with the appropriate event name. In
fact, I think all stock Zope objects should in the nearby future use the
Observable pattern to advertise events like this.

A catalog, or a specialist object can then react to those events by updateing
the catalog. This mechanism allows further refinement of what happens when an
object changes, allowing for complex indexing policies, where these policies
are contained and thus manageable within one object instance.

The pattern (implemented in a mixin class checked into the tree):

  http://www.zope.org/Members/michel/Projects/Interfaces/ObserverAndNotification

In fact, I like this way of managing catalogs better than the CatalogManager
proposals now in the Interfaces Wiki.

-- 
Martijn Pieters
| Software Engineer    mailto:mj@digicool.com
| Digital Creations  http://www.digicool.com/
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