Chris Withers wrote:
Philipp von Weitershausen wrote:
Utilities are never created when they're looked up. They're created
when registered. Singletons (instances) are registered with the
utility registry, never factories.
Ah, yes, of course, I think I'm looking for local utilities...
But even global utilities are *first* instantiated from their factory,
then registered as singleton instances.
and all I'm then doing with the list is generating a drop-down for
people to select from...
getUtilitiesFor is all we have. If you want that drop-down, consider
using UtilityVocabulary from zope.app.component.vocabulary, e.g.:
class FooUtilityNames(UtilityVocabulary):
interface = IFoo
nameOnly = True
classProvides(IVocabularyFactory)
Register that as a utility:
<utility component="...FooUtilityNames" name="Foo Utilities"/>
Then you can refer to it from a schema definition (Choice field).
Hmm, okay, how have the UI's for the creation of local utilities been
built? (I'm thinking there must be some kind of drop-down somewhere with
an "Add list" as in Zope 2's ZMI, and that must include the available
types of local utility?)
Sure. Just use the standard "Add" menu in Zope 3. Some of the items
there are potential local utilities, such as the Catalog, Cookie Client
Id Manager, Error Logging Utiltiy, etc. You can add these objects
anywhere, though it is recommended to do it within ++etc++site. The
thing that makes them available as utilities is the registration. All
objects have a "Registration" tab.
Also, more theoretically, would you see indexes for a catalog as being
local utilities. If not, what would you see them as being?
The catalog is the local utility. It functions as a container for
indices. The catalog employs object event subscribers that tell it when
objects have changed. THe catalog dispatches this action to its
contained indices. That's about all the catalog does in Zope 3. You'll
have to do everything else :).
Philipp
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