Chris Withers wrote: > Philipp von Weitershausen wrote: >> class IKeyReference(zope.interface.Interface): >> """A reference to an object (similar to a weak reference). >> >> The references are compared by their hashes. >> """ >> >> There, that wasn't so hard... > > Well yeah, but it's also not very explanatory ;-) > > If it's similar to a weak reference, why not just a weak reference? What > are the salient differences between a normal weak reference and a key > reference?
Basically, key references are things you can use as keys in dicts (hence the name). In other words, IKeyReferences provide a (unique) hash for an object. hash(IKeyReference(obj)) is just a fancy way of saying hash(obj). We need the fanciness because hash(obj) is meaningless for e.g. persistent objects or objects dynamically created from, say, a relational database. The IKeyReference adapter can be smarter about it and figure out what a good unique hash for the object is. E.g. the adapter for persistent objects hashes the database name and the object's oid. This cominbation is always unique on a system. Feel free adding this as a README.txt to zope.app.keyreference :) Philipp _______________________________________________ Zope3-users mailing list Zope3email@example.com http://mail.zope.org/mailman/listinfo/zope3-users