Ron Buckton wrote:
Perhaps Future should have a static Future.cancelable method (similar to
Proxy.revocable):
Matching the two APIs seems like a win, all else equal.
let { future, cancel } = Future.cancelable(function(resolver) { .. do future
stuff .. });
You would still need a means to hook cancellation, possibly by replacing cancel
to the caller:
function getJSON() {
var xhr = new XMLHttpRequest();
...
let { future, cancel } = Future.cancelable(...);
return { future, cancel: function() { cancel(); xhr.abort(); } };
}
The other advantage of the Proxy.revocable pattern, as Tom pointed out,
is its OCap-ness; you can't use the returned revoke on some other
revocable proxy. Same argument would apply to Future.cancelable.
/be
Ron
-----Original Message-----
From: es-discuss-boun...@mozilla.org [mailto:es-discuss-boun...@mozilla.org] On
Behalf Of Brendan Eich
Sent: Tuesday, April 23, 2013 6:41 PM
To: Tab Atkins Jr.
Cc: es-discuss
Subject: Re: Futures
Tab Atkins Jr. wrote:
On Sat, Apr 20, 2013 at 6:17 AM, Brendan Eich<bren...@mozilla.com> wrote:
Tab Atkins Jr. wrote:
It would be so nice if JS had multiple return values, so we could
let cancellable future-returning APIs just return a naked resolver
as their second value,
Hello, destructuring:
let{ proxy, revoke} = Proxy.revocable(target, handler);
from
http://wiki.ecmascript.org/doku.php?id=strawman:revokable_proxies. Or use an
array pattern if you prefer.
JIT'ing VMs can optimize these pretty easily to avoid object allocation.
Yeah, that's fine when you're explicitly invoking something that needs
to return two objects.
You didn't grok what I wrote. The object is erased, and the value(s) are
returned to the caller depending on the pattern it uses.
It's less fine when you have something like a hypothetical getJSON()
(future-returning XHR sugar), which can reasonably just return a
future, but which we also want to make cancellable. Burdening *every*
call site
No, you can use a smaller pattern, e.g.
let { future } = getJSON();
instead of
let { future, cancel } = getJSON();
with the need to pull out the future from the returned object
No, see above.
isn't great.
HTH.
/be
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