如何将变量绑定到 as3 中的 function

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.

Answer 2

Try this.

for each(var tool in tools){
  tool.addEventListener(MouseEvent.MOUSE_DOWN, toolFunction )
}

function toolFunction (e:MouseEvent){
  trace(e.currentTarget)
}

Aftear reading question title again, i realized, that what u need is custom event or:

for each(var tool in tools){
      tool.addEventListener(MouseEvent.CLICK,
              function(e:MouseEvent){toolFunction (e, "another param")},
              false, 0, true);
    }

    function toolFunction (e:MouseEvent,anotherParam:String){
      trace(e.currentTarget)
      trace(anotherParam) //output "another param"
    }

Answer 3

try to do:

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

Answer 4

You can't nest functions inside loops the parameters for the function call will have the same value across all iterations of the loop, and that value will be from the last most iteration. There are some hacks to handle this, but it is not good coding practice and makes it hard in the future to modify it.

What you need to do is more OOP style.

Since the Tool class is obviously custom you need to modify it to hold the values or whatever references you were talking about for the future.
Basically, if you have a value you need to pass along that is related to that object then just make that value an attribute of the class Tool.

Answer 5

use as3 signals

http://www.peterelst.com/blog/2010/01/22/as3-signals-the-best-thing-since-sliced-bread/

It can cater your problem nicely. Once I have tried signal I can't go back. It's much better than the event system in as3