Le 06/01/2012 12:23, Andrea Giammarchi a écrit :
it doesn't ... as soon as you release the reference to o no leaks
persists but of course until you keep o on hold those unique callbacks
cannot be released ...
If you're telling me that keeping only one of the object or the function
alive but not both keeps the bound function alive, then you do have a
leak. The bound function only has a reason to exist if both the object
and the function remain in the program.
but this would be true with WeakMap too, isn't it?
No it wouldn't. Since WeakMaps keep weak references, you can't have the
type of leaks I just described. As I said in [1], the bound function
will be kept in memory only if both the object and the function are
still strongly held somewhere (so the weakmap doesn't count).
In any case, boundTo is suitable for listeners and the whole point is
to do not hold manually those function
once again
window.addEventListener("whatever", o.boundTo(o.method), false);
// later on
window.removeEventListener("whatever", o.boundTo(o.method), false);
// that's it
We can reuse/add the listener later on without problems but as soon as
object "o" will be unreachable (no reference count === 0)
"Reference count === 0" and "unreachable" are different properties.
An object can be unreachable even with a reference count different of 0.
everything will be fine
This, versus this anti pattern
o._leMethodBound = o.method.bind(o);
window.addEventListener("whatever", o._leMethodBound, false);
// later on
window.removeEventListener("whatever", o._leMethodBound, false);
o._leMethodBound is exposed
only because of your implementation.
and used only to hold a bound method ... we have all done this until
now, and to me it's kinda illogical, boring, error prone
I fully agree with your use case. Yet, you still haven't answered my
question:
If browsers implemented your proposal, it would certainly be in new
versions that will certainly already have WeakMaps built-in. In this
case, what would be the benefit of a native implementation rather than a
library of yours?
Regarding your earlier argument about 'bind' being often implemented in
libraries, it has to be noted that ES5 version of bind has features that
ES3-based polyfill cannot emulate including being safe against
redefinition of 'call' and 'apply'.
David
[1] https://mail.mozilla.org/pipermail/es-discuss/2012-January/019306.html
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