Question

I have this code:

for each(var tool in tools){
tool.addEventListener(MouseEvent.MOUSE_DOWN, function(){
    trace(tool); //Always the last tool  
 });
}

How do I bind the value of tool to the function so that it’s accessible on callback?

Answer 1

You have to use a function inside a function to properly bind the scope. It’s kind of a hack in AS3. It’s better not to go down that rabbit hole if you can help it. If you must, though…

for(var tool:Tool in _tools){
  var getHandler(scope:Tool):Function{
    var t:Tool = scope;
    return function(e:MouseEvent):void{trace(t)}
  }
  tool.addEventListener(MouseEvent.CLICK, getHandler(tool));
}

EDIT: And of course, any variables you need to work with in the handler should be passed into getHandler as well… so instead of just accepting the scope param, you’d also pass your id, count, current state, or whatever.

EDIT2: But ask yourself this question. How will you remove that event listener? That’s the biggest reason I say to avoid this rabbit hole entirely. It’s possible, but it’s usually more trouble than using a more OOP way of solving this problem than lambda functions.