Object Method CallBack Reference

[Jayhoo]

I need to call back an Object method once another Object Event has Occured (DB connection return data, pass to handler and execute)

Similar to the setInterval script below:

setInterval( obj, "function", 1000 );

I want to specify the call back object and method when i call another Objects Method, this is then stored in a property and executed upon an event i.e. data returned

Am i making any sense?

I have attached a zip file of a demo selection of files that will explain it a bit further.

What is happening is on the call back the scope is of the initial caller not the recipient who needs to handle the data, hence the For loop traces the Callers Properties not the Recipients Object properties.

So my question (at last) is how does the setInterval function create a reference to the object and allow the correct scope when the method is called? As may example does not!

Any help with this would be much appreciated as it is the corner stone of a database dependant class library i am writing.


Cheers
JOn

[moagrius]

you can use the call and apply functions to reassign scope to arbitary objects.

functionname.call(objectreference,argument1,argmen t2);

apply is similiar, but accepts an array in the second arguments which are concatenated during execution into individual arguments

functionname.apply(objectreference,[argument1,argument2,argument3]);

setInterval can work just like anything else if you dont use the suggested syntax, but rather a standard function constructor

setInterval(function(){

//statements.. just like you'd do with an onPress or onEnterframe;

},1000);

[Lexicon]

I think for a class based project, Delegate is what you are after.

import mx.utils.Delegate;

var yak:Object = new Object();

yak.myFunc = function()
{
	trace("scope = "+this);
}

// var iv = setInterval(yak, 'myFunc', 1000);
var iv = setInterval(Delegate.create(this, yak.myFunc), 1000);

[Jayhoo]

Thanks for the replies, not used either scripts before I'll have a look and may come back with queries.

Did you have a look at the example code?
Just interested if either of you got it working with your solutions?

Thanks again
JOn

[Lexicon]

class ReturnSlave
{
	var correct_scope:Boolean;
	
	function ReturnSlave()
	{
		correct_scope = true;
	}
	
	public function recieve (Void):Void
	{
		var i:String;
		for(i in this)
		{
			trace(i+" = "+this[i])
		}
	}
}

swap the commented line for the Delegate line and you can see the scope switch....

class CallToReturn
{
	public var returnCall:Function;
	public var correct_scope:Boolean;
	
	function CallToReturn()
	{
		correct_scope = false;
	}
	
	public function callFunc (obj:Object, func:String):Void
	{	
		//returnCall = obj[func];
		returnCall = mx.utils.Delegate.create(obj, obj[func]);
		returnCall();
	}
	
}

[Jayhoo]

You are a star mate cheers (Both of you)

Have to delve a little deeper into the inbuilt classes. Where is this documented or just as intrestingly how did you find this?

Had a look at the Delegate.as file and using some code (arguments.callee.target) that i havent come across before....always more to learn i guess.

Thanks again

Jon

[Lexicon]

I found it by looking at the classes, it was a Eureka moment

It's all documented in help anyways.


You should look at the EventDispatcher class too. I think you might find that useful when you need callback functions too.