Topic awaiting preservation: objects, "this" and settimeout() (Page 1 of 1)

Recent posts on this stuff reminded me of something I've been wondering about.

Is there a way to reference objects using "this" when using a settimeout()?

ie.

function thing() {
this.i=0;
this.doSomething = function() {
this.i++
window.status=i;
setTimeout("myThing.doSomething()",20); // ideally "this" somehow?
}
}

var t = new Thing();
t.doSomething();

I've used arrays of objects before where each object is passed the index of the array it's in, so it's handy for if you need to reference back to the object from the outside (because of settimeout() or whatever) - but is there a better way around this?

- scott

Lotta these questions going around as of late

I'm a little confused though, are you sayign that using setTimeout("this.doSomething()",20); doesn't work?... I'm pretty sure it does... At least I was using "this" within a setInterval() call for an object.function()...

But you do realise that you won't be able to have 2 or more of those doSomething() timeout's running at the same time, regardless of weather or not their in seperate objects. As soon as you trigger another setTimeout() the first one will be stopped. Well, at least they are if you use "this" in the timeout call.

[This message has been edited by Dracusis (edited 01-19-2003).]

Nope the "this" in a setTimeout/setInterval doesn't work. There's no great solution for this, really... if it took a function as its argument rather than a string, it could be done somehow probably... but I don't know of an easy way. I rarely use setTimeouts that extensively.

Scott: I've been puzzled too by the fact that the setTimeout function is only available on the window object. So I throw the following piece of code :

function evalSetTimeout( evalString, delay )

{

    return eval( "setTimeout( \""+ evalString.replace( /this/gi, "document.objectsInstanceArray[ "+

 this.objectsInstanceArrayIndex +" ]" ) +"\", "+ delay + " )" )

}

function evalSetInterval( evalString, delay )

{

    return eval( "etInterval( \""+ evalString.replace( /this/gi, "document.objectsInstanceArray[ "+

 this.objectsInstanceArrayIndex +" ]" ) +"\", "+ delay + " )" )

}





function myClass( value )

{

    // SHARED INITIALIZATIONS OF THE CLASS

    if( !document.objectsInstanceArray )

        document.objectsInstanceArray = []

    this.objectsInstanceArrayIndex = document.objectsInstanceArray.length

    document.objectsInstanceArray[ this.objectsInstanceArrayIndex ] = this

    this.setTimeout = evalSetTimeout

    this.setInterval = evalSetInterval



    // SPECIFIC INITIALIZATION OF THE CLASS

    this.value = value



    this.doSomething = myClass_doSomething

    function myClass_doSomething( iteration )

    {

        document.body.innerHTML += "<hr>object #"+ this.objectsInstanceArrayIndex +"<br>value = "+

 this.value +"<br>iteration # "+ iteration

        if( --iteration>0 )

            this.setTimeout( "this.doSomething( "+ iteration +" )", 500 )

    }

}



myClassInstance1 = new myClass( "@___@" )

myClassInstance2 = new myClass( "zZZZZzz!" )



myClassInstance1.doSomething( 3 )

myClassInstance2.doSomething( 4 )

myClassInstance2.setTimeout( "alert( this.value )", 50  )

This little hack stacks the reference of the objects in a global array, overloads the setTimeout and setInterval by a function that evaluates a string in which the keyword this is replaced by the reference in the global array. I did that quickly so the parameters of the setTimeout & setInterval methods aren't well parsed

Indeed, having the setTimeout and setInterval methods available on any instances of your classes can be really handy.

Cheers,

Mathieu "POÏ" HENRI

[Emp edit: Killed HSBoD]

[This message has been edited by Emperor (edited 06-26-2003).]

I've been using the setTimeout within objects for quite a while now and I had always made the object name a member of the object that needed a setTimeout. Then I just called the timer using that. I have looked for alternatives for this and have not found any.

. . : slicePuzzle

I got a line from bratta a long time ago

function thing() {
this.i=0;
// Go these lines from bratta a long time ago.
this.obj = 'Object';
eval (this.obj +' =this');
this.doSomething = function() {
this.i++;
if (this.i <= 20) window.status = this.i;
setTimeout(this.obj+".doSomething()",20);
}
return this;
}



.:[ Never resist a perfect moment ]:.

Clever. With that, you only need to find a separate ID string for each object.