Access of possibly undefined property number through a reference with static type...

Question

Hello everyone !
I run into this problem today ... take a look on the code :
import com.trick7.effects.TeraFire;
for (var j:uint=0; j<10; j++) {
    var fire:TeraFire = new TeraFire();
    fire.x = j * 40 + 20;
    fire.y = 100;
    fire.number = j; //This line is causeing the problem
    addChild(fire);
    fire.buttonMode = true;
TeraFire class creates fire particles. The compiler error is :
Scene 1, Layer 'Layer 1', Frame 1, Line 7
1119: Access of possibly undefined property number through a reference with static type com.trick7.effects:TeraFire.
Anyone can help me to find a solution to this problem.
I can do that ".number" with a movieclip but not in this case. What can I do ?

Answer 1

I borrowed that class from the internet.
I made the changes you suggested: imported flash.Display.MovieClip and also made the class extend MovieClip.
The error is still throwing in compiler errors. I am not really good enough to edit this class because there are some functions I don't still understand very good. This is the class below:
package com.trick7.effects{
    import flash.display.BitmapData;
    import flash.display.GradientType;
    import flash.display.MovieClip;
    import flash.events.Event;
    import flash.filters.DisplacementMapFilter;
    import flash.filters.DisplacementMapFilterMode;
    import flash.geom.Matrix;
    import flash.geom.Point;
    import flash.geom.Rectangle;
    public class TeraFire extends MovieClip{
        public var phaseRateX:Number;
        public var phaseRateY:Number;
        private var offsets:Array= [new Point(),new Point()];
        private var seed:Number = Math.random();
        private var fireW:Number;
        private var fireH:Number;
        //火の色
        //private var fireColorIn:uint;
        //private var fireColorOut:uint;
        private var ball:Sprite;
        private var gradientImage:BitmapData;
        private var displaceImage:BitmapData;
        private var focalPointRatio:Number = 0.6;
        private const margin:int = 10;
        private var rdm:Number;
        public function TeraFire(xPos:Number=0, yPos:Number=0, fireWidth:Number=30, fireHeight:Number=90, fireColorIn:uint = 0xFFCC00,fireColorOut:uint = 0xE22D09){
            fireW = fireWidth;
            fireH = fireHeight;
            phaseRateX = 0;
            phaseRateY = 5;
            var matrix:Matrix = new Matrix();
            matrix.createGradientBox(fireW,fireH,Math.PI/2,-fireW/2,-fireH*(focalPointRatio+1)/2);
            var colors:Array = [fireColorIn, fireColorOut, fireColorOut];
            var alphas:Array = [1,1,0];
            var ratios:Array = [30, 100, 220];
            var home:Sprite = new Sprite();
            ball = new Sprite();
            ball.graphics.beginGradientFill(GradientType.RADIAL,colors, alphas, ratios, matrix,"pad","rgb",focalPointRatio);
            ball.graphics.drawEllipse(-fireW/2,-fireH*(focalPointRatio+1)/2,fireW,fireH);
            ball.graphics.endFill();
            //余白確保用透明矩形
            ball.graphics.beginFill(0x000000,0);
            ball.graphics.drawRect(-fireW/2,0,fireW+margin,1);
            ball.graphics.endFill();
            addChild(home);
            home.addChild(ball);
            this.x = xPos;
            this.y = yPos;
            addEventListener(Event.ENTER_FRAME,loop);
            displaceImage = new BitmapData(fireW+margin,fireH,false,0xFFFFFFFF);
            var matrix2:Matrix = new Matrix();
            matrix2.createGradientBox(fireW+margin,fireH,Math.PI/2,0,0);
            var gradient_mc:Sprite = new Sprite;
            gradient_mc.graphics.beginGradientFill(GradientType.LINEAR,[0x666666,0x666666], [0,1], [120,220], matrix2);
            gradient_mc.graphics.drawRect(0,0,fireW+margin,fireH);//drawのターゲットなので生成位置にこだわる必要はない。
            gradient_mc.graphics.endFill();
            gradientImage = new BitmapData(fireW+margin,fireH,true,0x00FFFFFF);
            gradientImage.draw(gradient_mc);//gradient_mcを消す必要は？
            rdm = Math.floor(Math.random()*10);
        private function loop(e:Event):void{
            for(var i:int = 0; i < 2; ++i){
                offsets[i].x += phaseRateX;
                offsets[i].y += phaseRateY;
            displaceImage.perlinNoise(30+rdm, 60+rdm, 2, seed, false, false, 7, true, offsets);
            displaceImage.copyPixels(gradientImage,gradientImage.rect,new Point(),null, null, true);
            var dMap:DisplacementMapFilter = new DisplacementMapFilter(displaceImage, new Point(), 1, 1, 20, 10, DisplacementMapFilterMode.CLAMP);
            ball.filters = [dMap];
I you can clarify a little bit further I would appreciate it a lot because I wasted some good time on this.