ActionScript3: how to initialize array length in object after it has been declared?

Question

I'm using an AS3 class that is:

package {
    public class PeopleInfo {
        public var elements:int;
        public var PeopleName:Array;
        public var PeopleInt:Array;
        public var PeopleDecimal:Array;
    }
}

In another file I've got:

<?xml version="1.0" encoding="utf-8"?>
<s:Application 
    creationComplete="initApp()"
    xmlns:fx="http://ns.adobe.com/mxml/2009"
    xmlns:s="library://ns.adobe.com/flex/spark"
    xmlns:mx="library://ns.adobe.com/flex/mx">

    <fx:Script>
        <![CDATA[
        public var ii:int;  

        public var dataWriteToDB:PeopleInfo = new PeopleInfo;

        public function initApp():void
        {
            // Initialize data provider array.

            var int_data:Array = new Array(10, 20, 30, 40, 50);
            var decimal_data:Array = new Array(13.11, 23.34, 35.69, 43.29, 58.92);
            var name:Array = new Array("Joe", "Karen", "Simon", "Greg", "Alice");

            dataWriteToDB.elements = 5; // number of elements in array

            for (ii = 0; ii < dataWriteToDB.elements; ii++)
            {
                dataWriteToDB.PeopleName[ii] = name[ii];
                dataWriteToDB.PeopleInt[ii] = int_data[ii];
                dataWriteToDB.PeopleDecimal[ii] = decimal_data[ii];
            } 

        }
and so on...

I'm getting a run-time error: Error #1009: Cannot access a property of method of a null object reference referring to the for loop's first line dataWriteToDB.PeopleName since it is NULL.

I'm guessing the problem here is that while dataWriteToDB is declared initially, the array lengths for the arrays in PeopleInfo class have not been set yet. Or, not sure otherwise why it's NULL. Anyone know how to clear this up?

laurent · Accepted Answer · 2012-02-24 15:56:26Z

1

The arrays have not been initialized in the class. You should do it in the declaration:

package {
    public class PeopleInfo {
        public var elements:int;
        public var PeopleName:Array = [];
        public var PeopleInt:Array = [];
        public var PeopleDecimal:Array = [];
    }
}

Also consider using push to add elements to the array, to avoid accidentally accessing a non-existing index:

        for (ii = 0; ii < dataWriteToDB.elements; ii++)
        {
            dataWriteToDB.PeopleName.push(name[ii]);
            dataWriteToDB.PeopleInt.push(int_data[ii]);
            dataWriteToDB.PeopleDecimal.push(decimal_data[ii]);
        }

answered Feb 24, 2012 at 15:56

laurent

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