> -----Original Message-----
> From: Dan G. Switzer, II [mailto:[EMAIL PROTECTED]
> Sent: Tuesday, March 21, 2006 11:10 AM
> To: CF-Talk
> Subject: RE: JavaScript Scoping Gurus?
>
> Jim,
>
> What I've always done to counter this problem is to create an API
> class--which I use to monitor instances of each class and hold "global"
> functionality. For example:
Thanks... but I really hate "tainting" the global scope if I can at all help
it.
I think I've found an answer however. The problem is that "setInterval()"
runs in context of the window object and that the code sent to it is treated
as a string (it's evaluated every time it's run) so "this" can't be passed.
Instead you can force lexical scoping to be honored by using a proxy
function in the scope of the object - the function reference maintains its
scope since it's "pinned" to the context in which it was created.
Here's how I ended up doing it:
// Create the Pool
function HTTPRequestPool(ObInstanceCount, IntervalCount) {
... lots of other code ...
// Set a proxy function to maintain scoping when called in
the context of Window
var ThisPool = this;
var IntervalProxy = function() { ThisPool.doRequest() };
// Start the Interval
window.setInterval(IntervalProxy, IntervalCount);
};
This works a treat.
Note that it's pretty "fragile" in the sense that all those parts are
needed. Doing the following doesn't work:
var IntervalProxy = function() { this.doRequest() };
window.setInterval(IntervalProxy, IntervalCount);
This doesn't work either (because you must pass a reference to the function
rather than the function call):
var ThisPool = this;
var IntervalProxy = function() { ThisPool.doRequest() };
window.setInterval(IntervalProxy(), IntervalCount);
It's like you have to "pin" and reinforce the reference to the object at
every step.
Considering that I don't feel so bad that it took a while for me to get it.
;^)
Jim Davis
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