On Thu, Apr 29, 2010 at 11:51 AM, Mark S. Miller <[email protected]> wrote: > On Thu, Apr 29, 2010 at 12:25 AM, Alex Russell <[email protected]> wrote: >> >> node.addEventListener("click", bang(obj, "method")); >> // works! >> node.removeEventListener("click", bang(obj, "method")); > > On Thu, Apr 29, 2010 at 10:42 AM, Tom Van Cutsem <[email protected]> wrote: >> >> node.addEventListener("click", bind(obj).method ); >> node.removeEventListener("click", bind(obj).method ); > > Both techniques cache the bound method, in order to preserve identity, so > that the above examples work. > When caching, one should always worry about cache invalidation. Say that obj > inherits from Foo.prototype and that both examples are thereby caching > Foo.prototype.method as bound to obj. Neither Alex nor Tom are first > verifying that Foo.prototype.method is a non-writable, non-configurable data > property, and so neither are justified in assuming its value may not change. > Between the two statements above, what happens if > Foo.prototype.method = function(){ /* some other function */ }; > ? Because Alex's cache is indexed by the identity of obj and by the name > "method", bang will return a stale result and the removeEventListener will > succeed when it shouldn't. Because Tom's cache is indexed by the identity of > obj and the identity of the function being bound, the removeEventListener > will properly fail. > I verbally verified with Tom just now that he hadn't thought about this > cache invalidation issue at all. I think this corroborates that the > EphemeronTable-based technique is more robust -- it did the right thing for > the right reasons even for cases that weren't thought about at the time. (Of > course, no matter how robust the patterns being used, please *always* think > about cache invalidation when designing a cache of any kind.)
I'm arguing for a syntax, not a particular implementation. The one I provided was only to illustrate (briefly, if that's at all possible) how such a thing might work. The *last* thing I want is an actual bang() or bind() method to be carted around the network in source form. That's the failure I'd like us to finally start avoiding. _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
