Hi Tab, thanks for a concrete example. From previous experience in E with similar promises, I agree that registering handlers later is quite natural, but I didn't have time to hunt for an example.
It would indeed be silly to require such a counter-intuitive freshness workaround in order to avoid a counter-intuitive diagnostic. On Thu, Apr 18, 2013 at 9:43 AM, Tab Atkins Jr. <[email protected]>wrote: > On Thu, Apr 18, 2013 at 9:14 AM, Kevin Smith <[email protected]> wrote: > >>> Also, can someone point me to a real-world example of delayed rejection > >>> handling? > >> > >> What do you mean by "delayed"? If that is: a promise has been rejected > and > >> someone later add a .fail/.catch handler to it, then I've never done > that > >> personally. > > > > > > Yes, that's what I mean. Specifically, a real-world example where the > > rejection handler is added in "some future turn", using a fuzzy > definition > > of that phrase. A contrived example would be: > > > > // Create a future and get the resolver > > let resolver, future = new Future(r => resolver = r); > > > > // Reject it > > resolver.reject("error"); > > > > // Attach a rejection handler 5 seconds later > > setTimeout(() => future.then(null, err => null), 5000); > > There are several DOM APIs planning to use Futures which will return > the same future across multiple calls. This future may have been > rejected in a previous turn. > > An example of this is the Font Load API built with Futures that I'm > currently proposing: <http://www.xanthir.com/b4PV1>. The Font#ready > function tracks the loading status of a single @font-face rule, so it > just returns the same future over and over. > > These kinds of APIs *could* be done by tracking future state > internally, and always returning a fresh future matching the internal > state, but that seems silly. > > ~TJ > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss > -- Text by me above is hereby placed in the public domain Cheers, --MarkM
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