CODEWITHSUNDEEP
actionscript-3flash
DomingoSL
DomingoSL

Reputation: 15504

Calling certain functions whitout having the right arguments

I have two function on my AS3 program, one fires when the width and height changes:

stage.addEventListener(Event.RESIZE, resizeListener);
function resizeListener (e:Event):void { 
//some commands
}

And the second one fires one a number of milliseconds pass:

var myTimer:Timer = new Timer(clockUpdate, 0);
myTimer.addEventListener(TimerEvent.TIMER, updateData);
myTimer.start();

function updateData(e:TimerEvent):void {
    trace("AUTOUPDATE");
    trace(e);
}

I need to fires those function also manually, lets say when the user press a button, but i don't know what parameters i have to send them when they are called manually.

I tried just resizeListener() and updateData() but of course it fails asking me for the parameter.

Upvotes: 0

Views: 69

Answers (2)

Lars Blåsjö
Lars Blåsjö

Reputation: 6127

Making the Event parameter optional, resizeListener(e:Event=null), as in walkietokyo's answer, is a perfectly valid and often convenient solution. Another alternative is to put the stuff you want to be able to do without the event being triggered in a separate function, that can be called by the event handler and from anywhere else.

So assuming for example that what you want to do on resize is to rearrange the layout, and you also want to do that same layout setup at initialization, or at the click of a button, or anytime really, you could do something like this:

stage.addEventListener(Event.RESIZE, resizeListener);
function resizeListener(e:Event):void { 
   rearrangeLayout();
}

function rearrangeLayout():void {
   // The actual rearrangement goes here, instead of in resizeListener. This can be called from anywhere. 
}

Which way to do it is probably a matter of taste or can vary from case to case, really, both works fine.

A benefit of separating things in an event handler and another function is that there will not arise a situation where you would have to check if the e:Event parameter is null or not. In other words, you would have code that is dependent on the Event, if any, in the event handler, and code that is independent of the Event in a more general function (not an event handler).

So in a more general and schematic case, the structure would be something like this:

addEventListener(Event.SOME_EVENT, eventListener);
function eventListener(e:Event):void { 
   // Code that needs the Event parameter goes here (if any).
   // Call other function(s), for the stuff that needs to be done when the event happens.
   otherFunction();
}

function otherFunction():void {
   // Stuff that is not dependent on the Event object goes here, an can be called from anywhere.
}

Upvotes: 1

david.emilsson
david.emilsson

Reputation: 2331

You can make parameters in a function optional by providing a default value. This is an example by taking your two functions above and making the event parameters optional:

function resizeListener(e:Event = null):void { 
    //some commands
}

and

function updateData(e:TimerEvent = null):void {
    trace("AUTOUPDATE");
    trace(e); 
}

Calling, for example, resizeListener() will now execute the function and the value of e will default to null.

Upvotes: 3

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