Object.observe would fit under "after" correct?
On Wed, Nov 28, 2012 at 4:09 PM, Tom Van Cutsem <tomvc...@gmail.com> wrote: > 2012/11/26 Dean Tribble <dtrib...@gmail.com> > >> On Mon, Nov 26, 2012 at 11:33 AM, Tom Van Cutsem <tomvc...@gmail.com>wrote: >> >>> Thanks for spelling out these examples. While they still don't feel like >>> actual important use cases to support, they give a good flavor of the kinds >>> of compromises we'd need to make when turning to notification-only proxies. >>> >> >> I agree. My usual expectation for proxies is to support remote and >> persistent objects. While supporting other scenarios is great, usually >> that's incidental. Is there a broader list of aspirations for proxies? or >> is this just a "all else being equal it would be good if we can do this"? >> > > Let's talk about aspirations for proxies. It will help us set priorities. > > First, some terminology (originating from CLOS, the "mother of all MOPs" > ;-) > CLOS method combinations allow a composer to distinguish between "before", > "after" and "around"-style composition: > - "before"-style wrapping gives you only the ability to get notified > before an operation happens. You can abort, but not change, the result of > the operation. This is what notification-proxies offer. > - "after"-style wrapping allows you to get notified of an operation > after-the-fact. Depending on the API, the "after"-wrapper may or may not > get to see the outcome of the operation, and may or may not change the > final outcome passed on to clients. > - "around"-style wrapping is the most general and allows the composer to > decide if and when to forward, and what result to return. It subsumes > before/after wrapping. This is what direct proxies currently provide. > > As far as I can tell, virtual object abstractions like remote/persistent > objects require "around"-style wrapping, because there's otherwise no > meaningful target to automatically forward to. > > Here's a list of use cases that I frequently have in mind when thinking > about proxies, categorized according to whether the use case requires > before/after/around wrapping: > > Virtual objects, hence "around"-style: > - self-hosting "exotic" objects such as Date, Array (i.e. self-host an > ES5/ES6 environment) > - self-hosting DOM/WebIDL objects such as NodeList > > Around-style wrapping (need to be able to change the result of an > operation): > - membranes > - higher-order contracts > > Before-style wrapping: > - revocable references > > What else? > > Cheers, > Tom > > _______________________________________________ > es-discuss mailing list > es-discuss@mozilla.org > https://mail.mozilla.org/listinfo/es-discuss > >
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