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:
function _HRPApi(){
this.instance = [];
}
_HRPApi.prototype.register = function (obj){
var iInstance = this.instance.length;
this.instance[iInstance] = obj;
return iInstance;
}
// create the global class
HTTPRequestPoolApi = new _HRPApi();
Now in your actual class, you can do something like:
function HTTPRequestPool(){
this.instance = HTTPRequestPoolApi.register(this);
this.interval = 500; // number of ms to wait before setTimeout
}
Now, anytime you need to reference the current instance of the class from a
global function (such as inside the setTimeout) you've got a copy stored in
a global variable (HTTPRequestPoolApi) you can access it with something like
the following code:
setTimeout(
"HTTPRequestPoolApi.instance[" + this.instance + "].method();",
this.interval
);
Hope this helps!
-Dan
>-----Original Message-----
>From: Jim Davis [mailto:[EMAIL PROTECTED]
>Sent: Tuesday, March 21, 2006 10:37 AM
>To: CF-Talk
>Subject: OT: JavaScript Scoping Gurus?
>
>I'm building an HTTP request pooler in JS. In essence the pool creates
>several HTTP objects and allows the programmer to add requests to the
>queue.
>The queue is then examined at an interval and queued requests are passed to
>free objects for calls.
>
>Anyway - all that seems to work pretty well - except setting up the
>interval.
>
>Let's assume this simplified Object:
>
> // Create the Pool
>function HTTPRequestPool(ObInstanceCount, IntervalCount) {
>
> // Create a Queue for Requests
> this.RequestQueue = new Array();
>
> App.RequestPoolTimer = window.setInterval("this.doRequest();", 500);
>
>};
>
>HTTPRequestPool.prototype.addRequest = function addRequest( Method, URL,
>Parameters, Handler) { };
>
>HTTPRequestPool.prototype.doRequest = function doRequest() { };
>
>
>We would instantiate this like this (someplace on the page):
>
>RequestPool = new HTTPRequestPool(5, 500);
>
>The problem is the interval - in this case the doRequest() method, when
>called from the interval, loses the connection to the parent object. When
>called "this" refers to the top-level window (as it would when a top-level
>function is called) NOT to the parent object (as it would when a method is
>called).
>
>However if I remove the interval from the object and instantiate things
>like
>this (setting the interval outside of the object):
>
>RequestPool = new HTTPRequestPool(5, 500);
>App.RequestPoolTimer = window.setInterval("RequestPool.doRequest();", 500);
>
>Everything works fine - the interval never loses its reference.
>
>This is a workaround, but I'd much rather have the interval contained in
>the
>object itself.
>
>Thanks in advance for any ideas.
>
>Jim Davis
>
>
>
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