Question

I have already set a variable in my document class “Main.as”. I am now trying to access that variable and read its value from a different Class and Function, take that value and email it.

For example in my “Main.as” file I have this function:

public var _myVar:String;

function create() {
    _myVar = "hello";
}

Now from my other class “EmailtoFriend.as” I have a new function to try and get the value of that pre set variable:

function getVar() {
    trace(_myVar);
}

Why will it not output “hello”? Instead I get an error saying: Access of undefined property _myVar. If I could just get this simple example working, I think it will help me understand a lot of things. Thanks!

Answer 1

The error your getting really says it all. Although _myVar is defined in your Main class public var _myVar:String;, it isn’t defined in your Emailtofriend class. If you want access to _myVar you need to do one of the following:

Parse a reference of your Main object(using this) to your EmailToFriend class:

Main.as(document class):

package 
{
    import flash.display.Sprite;
    import flash.events.Event;

    public class Main extends Sprite 
    {
        public var _myVar:String;

        public function Main():void 
        {
            if (stage) init();
            else addEventListener(Event.ADDED_TO_STAGE, init);

        }// end function

        public function create():void
        {
            _myVar = "hello";

        }// end function

        private function init(e:Event = null):void 
        {
            removeEventListener(Event.ADDED_TO_STAGE, init);

            create();

            var emailToFriend:EmailToFriend = new EmailToFriend(this);
            emailToFriend.getVar();

        }// end function

    }// end class

}// end package

internal class EmailToFriend
{
    private var _main:Main;

    public function EmailToFriend(main:Main)
    {
        _main = main;

    }// end function

    public function getVar():void
    {
        trace(_main._myVar);

    }// end function

}// end class

Or to make _myVar a public static property of Main and access it via Main._myVar:

Main.as(document class):

package 
{
    import flash.display.Sprite;
    import flash.events.Event;

    public class Main extends Sprite 
    {
        public static var _myVar:String;

        public function Main():void 
        {
            if (stage) init();
            else addEventListener(Event.ADDED_TO_STAGE, init);

        }// end function

        public function create():void
        {
            _myVar = "hello";

        }// end function

        private function init(e:Event = null):void 
        {
            removeEventListener(Event.ADDED_TO_STAGE, init);

            create();

            var emailToFriend:EmailToFriend = new EmailToFriend();
            emailToFriend.getVar();

        }// end function

    }// end class

}// end package

internal class EmailToFriend
{
    public function EmailToFriend() {}

    public function getVar():void
    {
        trace(Main._myVar);

    }// end function

}// end class

Also one small thing, when using underscores for class properties, you should only use them for private properties, not public. Well I say only but I really mean it’s more common.

[UPDATE]

This is in response to your comment:

Main.as:

package 
{
    import EmailToFriend;
    import flash.display.Sprite;
    import flash.events.Event;


    public class Main extends Sprite 
    {
        public static var _myVar:String;

        public function Main():void 
        {
            if (stage) init();
            else addEventListener(Event.ADDED_TO_STAGE, init);

        }// end function

        public function create():void
        {
            _myVar = "hello";

        }// end function

        private function init(e:Event = null):void 
        {
            removeEventListener(Event.ADDED_TO_STAGE, init);

            create();

            var emailToFriend:EmailToFriend = new EmailToFriend();
            emailToFriend.getVar();

        }// end function

    }// end class

}// end package

EmailToFriend.as:

package  
{
    import Main;

    public class EmailToFriend 
    {
        public function EmailToFriend() {}

        public function getVar():void
        {
            trace(Main._myVar);

        }// end function

    }// end class

}// end package