Tres Seaver wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > Gary Poster wrote: >> On Nov 27, 2009, at 6:32 AM, Martijn Faassen wrote: > >>> Utility lookups versus adapter lookups >>> -------------------------------------- >>> >>> There was some discussion on whether utility lookups are really >>> something fundamentally different than adaptation as adaptation >>> *creates* a new instance while utility lookup uses a registered >>> instance. I think the essential part here is however: "give me an >>> instance that implements IFoo", and utility lookup fits there. We could >>> even envision a way to create utilities that *does* instantiate them on >>> the fly - it shouldn't affect the semantics for the user of the utility. >> As above, I disagree. > > The root of the disagreement here is that you seem to want the *caller* > to care about something which is important only to the person who > *registers* the thing being looked up. From the caller's perspective, > the call site needs an object implementing IFoo, looked up using some > number N of context arguments, where N could be 0 (no context required > to find the object). The fact that, under the hood, an adapter lookup > happens to call a factory, passing the context args, is not relevant *to > the caller*.
I understand that the idea explained above is conceptually integral to a lot of people, and basically unquestionable. But as devil's advocate sort of thing can we put this traditional worldview aside for a minute, and just sort of take this from ground zero? In "normal Python", callers often do need to understand whether the function they're calling is a factory which constructs a new object, or a function which returns a "global", because the caller needs to know what the impact of mutating the result is. We call non-factories utilities and we call factories adapters. So the caller *already* needs to make a distinction between the two. - C _______________________________________________ Zope-Dev maillist - Zope-Dev@zope.org https://mail.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - https://mail.zope.org/mailman/listinfo/zope-announce https://mail.zope.org/mailman/listinfo/zope )