[Dojo-interest] Closures and memory usage (was: Widgets and memory issues)

Ed ednotover at gmail.com
Mon Feb 5 14:52:37 MST 2007


> From: Robert Coup <robert.coup at onetrackmind.co.nz>



Another option is to do something like this:
>
> function setupStuff(elements, handlerMessage) {
>     var handler = function() {
>        alert(handlerMessage);
>     }
>
>     var eLen = elements.length
>     for (var ii=0; ii<eLen; ii++) {
>        dojo.event.connect(elements[ii], "onclick", handler);
>     }
> }
>
> The handler function is therefore local in scope to setupStuff, but also
> has the benefits of being a closure (ie. it can access handlerMessage).




From: "Karl Tiedt" <ktiedt at gmail.com>




> Except in this case I believe:
>
>    for (var ii=0; ii<eLen; ii++) {
>       dojo.event.connect(elements[ii], "onclick", handler);
>    }
>
> Will connect all your events to elements[elements.length-1] due to lack of
> closure there ;)
>
> I think anyways from my experience that that would be the case. hehe
>


I thought about this for a while, and I don't follow the logic.  So I coded
it up and it works as Rob describes (and as I expected), where the handler
function is connected to each element in the elements array.

I certainly follow that if we were redefining the handler function within
the loop, then we'd have each element tied to the final handler definition -
the final function definition will be the retained closure.  Is that what
you meant, or am I missing something fundamental here?

Ed
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