Question

I have a small loop

var a:Array = [{name:Test1},{name:Test2},{name:Test3},{name:Test4}]
var b:GenericButton; //A pretty basic button component

for(var i:int = 0; i < a.length; i++){
  b = new GenericButton(a[i].name, function():void { trace(i) });
  this.addChild(b);
}

The function supplied to the GenericButton is executed when the button is pressed.

The problem I am having is that when the no matter what button I press the value of 4 (the length of the array) is always output.

How would I ensure that I trace 0 when the first button is pushed, 1 when the second is pushed, etc?

Answer 1

Well, you can simply do:

var f:* = function():void { trace(arguments.callee.index) };
f.index = i;
b = new GenericButton(a[i].name, f);

Better still:

function createDelegate(obj:Object, func:Function):Function
{
    var f:* = function ():* {
        var thisArg:* = arguments.callee.thisArg;
        var func:* = arguments.callee.func;

        return func.apply(thisArg, arguments);
    };

    f.thisArg = obj;
    f.func = func;

    return f;
}

…

for (...) {
      b = new GenericButton(a[i].name,
          createDelegate({index: i}, function():void { trace(this.index) }));
}

And in some (most?) cases it would be even better if you created a separate class and passed i into the constructor.