Question

I am encountering a strange problem. I am trying to generate a matrix with value of elements either 1 or 0 (filled randomly). I am storing the values into a 2D array. This is code on the first frame. Everything seems to be working fine.

var multiArr:Array = new Array([2], [2]);


    function generateMatrixXML() {

    for(var i:uint = 0; i < 2; i++)
    {
        for(var j:uint = 0; j < 2; j++)
        {
            multiArr[i][j] = getRandomNumber(0,1);;

        }
    }
    trace(multiArr);
    }

    function getRandomNumber(lower,upper):Number {
        return Math.floor(Math.random()*(1+upper-lower))+lower;
    }


    generateMatrixXML();

When I change the value of row and column to 3 I get an error.

var multiArr:Array = new Array([3], [3]);


function generateMatrixXML() {

for(var i:uint = 0; i < 3; i++)
{
    for(var j:uint = 0; j < 3; j++)
    {
        multiArr[i][j] = getRandomNumber(0,1);;

    }
}
trace(multiArr);
}

function getRandomNumber(lower,upper):Number {
    return Math.floor(Math.random()*(1+upper-lower))+lower;
}


generateMatrixXML();

TypeError: Error #1010: A term is undefined and has no properties.
at matrixArray_fla::MainTimeline/generateMatrixXML()
at matrixArray_fla::MainTimeline/frame1()

Got any idea as to what is the reason for error

Answer 1

This line:

var multiArr:Array = new Array([3], [3]);

Is creating an array containing two arrays, each of which has one element containing the number 3. That means that when you get to the third iteration multiArr[i] is undefined. This is clearly a misunderstanding of how to define arrays in AS3¹

You actually need to create your arrays within the loop:

var multiArr:Array = [];
var iterations:int = 3;

function generateMatrixXML() {
    for(var i:uint = 0; i < iterations; i++)
    {
        multiArr[i] = [];
        for(var j:uint = 0; j < iterations; j++)
        {
            multiArr[i][j] = getRandomNumber(0,1);

        }
    }
    trace(multiArr);
}

function getRandomNumber(lower,upper):Number {
    return Math.floor(Math.random()*(1+upper-lower))+lower;
}

generateMatrixXML();

Footnote 1: Flash coding practises require you to define a new array with the [] notation:

var arr1:Array = []; // create a new array
var arr2:Array = [1]; // create an array with  one element, the number 1
var arr3:Array = new Array(1); // defines a new array with a pre-set length of 1
var arr4:Array = new Array(1,2); // defines a new array with two elements, the numbers 1 and 2

The last example is considered a bad coding practise in AS3 because of the confusion it causes with the third example.