CallbackCollection-AS3

public class CallbackNumber{
    public function CallbackNumber(val:Number){
        _value = val;
    }
    private var _value:Number;
    private var callbacks:Array = new Array[];
    public function addCallback(callback:Function):void{
        if (callback == null)
            return;
        callbacks.push(callback);
    }
    public  function triggerCallbacks():void{
        for (var i:int = 0; i < callbacks.length; i++){
            callbacks[i].apply();
        }
    }
    public function getValue():Number{
        return _value;
    }
    public function setValue(val:Number):void{
        if(_value != val){
            _value = val;
            triggerCallbacks();
        }
    }
}
// -------- test Code ----------//
var num1:CallbackNumber = new CallbackNumber(1);
var num2:CallbackNumber = new CallbackNumber(2);
num1.addCallback(function():void{trace("num1's Callback called");});
num2.addCallback(function():void{trace("num2's Callback called");});
num2.setValue(22) // num2's Callback called

// Test - 1
num2.addCallback(function():void{trace(num1.getValue());});
num2.setValue(8)
// num2's callback called
// 1