Comments on: AS3 Best Practice for Callback Evals

By: John Kanding

John Kanding — Fri, 19 Mar 2010 23:27:59 +0000

Hmmm, I’m a bit confused as to why use a callback in the above situation. It seems not to wait for doing anything, just runs through the code. So why not just have

private function gameEnded():void {
saveScore(10);
onSave()
}
But anyway callBacks are nice and it’s good way it’s shown above. Never thought of it like passing a function directly… doooh!

I often do it like this:

One object is using another object and needs to be called back when that object is done:

myObj1.mLoadImage(“pic.png”, this, “mImDoneLoading”)

The mLoadImage function looks like this:

public function mLoadImage(image:String, cbObj:Object, cbMethod:String){

pCallBackObj = cbObj
pCallBackMethod = cbMethod

}

Whenever the image is loaded and everything is fine, it calls pCallBackObj[pCallBackMethod]()

This can be in a totally different function within that object.

By: ayu

ayu — Sun, 07 Feb 2010 18:00:40 +0000

callbacks are 4x-8x times faster than event listeners in performance. event listeners creates unnecessary object, each time it creates it bogs down the CPU,

By: Danny Miller

Danny Miller — Sat, 28 Feb 2009 00:37:03 +0000

Callbacks are fine but sort of the old way to do things… You should really use event listeners as that supports multiple “call backs” for a specific object.

By: Tyler Wright

Tyler Wright — Sat, 14 Feb 2009 16:08:06 +0000

The most common way to handle this type of comparison:

if(onSaveCallback != null) onSaveCallback()

…just a little easier.

By: pleclech

pleclech — Sat, 14 Feb 2009 14:42:15 +0000

Hello,

First sorry for my bad English…

My 2 cents, it seems a bit overkill just to test nullity of a function, since the short way make flash compiler complained, try the explicit way:

function foo(bar:Function=null):void{
if (bar!=null)
bar();
}

It will be faster than cast to an object and then compare to a string.

Regards.

By: Antoine

Antoine — Sat, 14 Feb 2009 13:06:11 +0000

Why not just do this test :

if(onSaveCallback != null) onSaveCallback();

By: Al

Al — Sat, 14 Feb 2009 12:17:18 +0000

How about using ‘is’:

if(onSaveCallback is Function) onSaveCallback();

Can’t help thinking a custom event is even cleaner…

By: Mije

Mije — Sat, 14 Feb 2009 08:33:46 +0000

Hm. Why not do this simple check?

if(onSaveCallback !== null) onSaveCallback();

By: Theo Denovan

Theo Denovan — Sat, 14 Feb 2009 08:09:59 +0000

I believe the following also works:

if( functionArg is Function )

By: Nick Schneble

Nick Schneble — Sat, 14 Feb 2009 07:09:38 +0000

There’s actually an easier solution-

Instead of:
if(onSaveCallback) onSaveCallback();

Do this:
if(onSaveCallback != null) onSaveCallback();