AS3 variable declaration

Sorry, AS3 noob question!

Assume that we have a movieclip:

var MC:MovieClip = new MovieClip();
addChild (MC);

Set variable values without declaration in this way:

MC.myString = "XXX";
MC.myNumber = 123;
MC.myMC = new MovieClip();

Is this legal in AS3 ? This doesn’t declares data type. Will this cause performance issues or conflicts?

Hi,

no, that’s fine… they will be casted as generic Objects.

keep in mind that you can save values like that only through instances of a dynamic class (MovieClip in this case).

Parker

VF said
Is this legal in AS3 ? This doesn’t declares data type. Will this cause performance issues or conflicts?

MovieClip is dynamic class which means you can add properties at runtime (like you did in your example)
untyped vars are allowed in AS3 , they don’t impact preformances as long as you’re not accessing them several thousands of times per frame.

Obviously,

if you use a generic class like MovieClip for your objects the only way to save some instance variables is that one.

When you’ll be more skilled about OOP you will create your own objects with classes that extend a base class and in that case

MC.myString = “XXX” will be handled by a setter that edit the instance variable _my_string for example…

Using setters and getters allow you to check that the data saved into these variables have the right format and type.

This would be good OOP for your case:

package {

    import flash.display.MovieClip;

    class MyClass extends MovieClip {

        private var _my_string:String;

        //getterfor _my_string

        function get myString():String {

            return _my_string;

        }

        //setter for _my_string

        function set myString(value:String):void {

            _my_string = value;

        }

        function MyClass() {

            //constructor

        }

    }

}

var mc:MyClass = new MyClass();

mc.myString = "XXX";

//to get the value just:

trace(mc.myStyring);

Parker

Nico is right using getters and setters is a great technique, here’s a great tutorial by Dru Kepple where you can learn more about them http://active.tutsplus.com/tutorials/actionscript/as3-101-oop-inheritance-setters-getters-basix/

Hope this helps – it helped me a lot

Thanks parker and bitfade, really helpful!

DaniMun, thanks for the link.

DaniMun said
Nico is right using getters and setters is a great technique

Coming from AS2 as my first scripting language, these were foreign to me. I realize you can execute things inside a getter or a setter, but you can also just call an internal function if you want to execute additional things, and then just change or return the property that you would have with the getter or setter. Personally I find it a lot easier to just use internal vars. I’m pretty sure it’s faster as well

VF said
Thanks parker and bitfade, really helpful! DaniMun, thanks for the link.

Don’t mention it, Ramesh, glad I could help

CrackerJack said

DaniMun said
Nico is right using getters and setters is a great technique

Coming from AS2 as my first scripting language, these were foreign to me.

Actually AS2 OOP allows for getters and setters usage

http://www.flashscript.biz/MX2004/OOP_tutorial/lesson5.html