Is it possible to pass an argument to the function triggered by an event handler?

Question

Hello All,
Trying to migrate my way of thinking from AS2 to CS4/AS3.
Ok, I have 2 buttons on the stage. Each button does almost
the same thing, so I want to create a single function, and each
button calls that same function (we'll name that function
"Navigate")... however, the function will need to end up doing
something different dependant on which button was clicked.
So, previously, in AS2, I would've added some code onto the
buttons themselves with on(release) methods (see CODE EXAMPLE 1)
So, each button effectively calls the Navigate function, and
passes a different frame label to the function.
Now, I'm trying to recreate this functionality in AS3. As you
all know, on(release) has been done away with (still don't know
why), but we now have to use event handlers, so I'm trying to
figure out a way to pass a different frame label argument to the
Navigate function. Currently I can achieve that by using a switch
statement to test which button was clicked, and act accordingly
(see CODE EXAMPLE 2).
In this over-simplified example, this works fine, but in the
real world I'm going to have more than 2 buttons, and the Navigate
function would probably be much more complicated...
So, I would like to be able to pass an argument(s) (like in
the AS2 example) to the Navigate function... perhaps in the
addEventListener() method? I tried this, but got compiler errors
(see CODE EXAMPLE 3):
The Million Dollar Question:
Is it possible to dynamically pass/change an argument(s) to a
function which is triggered by an event listener? (Or is the event
that triggered the function the only argument you can have?)
If this isn't possible, I'd greatly like to hear how you
folks would handle this (other than having a switch statement with
12 cases in it)???

Answer 1

I've found a couple solutions that I'll post below for
prosperity...
You could create a Dictionary keyed by the prospective event
targets and store any information in there you want associated with
them. Then the navigate function can check that dictionary to get
it's parameters:
// Code //
Button1.addEventListener(MouseEvent.CLICK, Navigate, false,
0, true);
Button2.addEventListener(MouseEvent.CLICK, Navigate, false,
0, true);
var buttonArgs:Dictionary = new Dictionary();
buttonArgs[Button1] = "FrameLabel1";
buttonArgs[Button2] = "FrameLabel2";
function Navigate(e:MouseEvent):void{
gotoAndStop(buttonArgs[e.target]);
This in my eyes, is about the same amount of work as writing
a long switch statement, but a little more elegant I suppose.
I had a little trouble understanding the next solution,
because I didn't quite understand an important piece of information
about event listeners. The addEventListener () requires a Function
as the 2nd argument passed to it.
It didn't quite click until someone pointed it out to me:
Navigate is a Function...
Navigate("FrameLabel1") is a Function
call...
So by writing just
Navigate, I'm not actually calling the function at the time
of the addEventListener call, I'm just supplying the event listener
with a reference to the name of the function. Then, when the
listener is triggered, the listener will call (and pass a
MouseEvent argument to) the Navigate function.
Conversely, by writing
Navigate("FrameLabel1") as the 2nd argument, the event
listener trys to execute the Navigate function at the time the
addEventListener is instantiated. And, since, in this example, the
Navigate function returned as ":void" a compile error would occur
because as I stated, an event listener requires a Function data
type as the 2nd argument. This would basically be like writing
addEventListener(MouseEvent.Click,
void, false, 0, true)
However, there is a way around this... basically, instead of
defining the Navigate function as returning a void data type, you
define it as returning a Function data type, and then nest another
function (which actually contains the actions you want to perform)
inside of it.
Button1.addEventListener(MouseEvent.CLICK,
Navigate("FrameLabel1"), false, 0, true);
Button2.addEventListener(MouseEvent.CLICK,
Navigate("FrameLabel2"), false, 0, true);
function Navigate(myLabel:String):Function{
return function(evt:MouseEvent):void{
gotoAndStop(myLabel);