Making a simple chase AI in AS3 - actionscript-3

Question

im attempting to make a simple game where zombies spawn out randomly from the edges of the screen and once they have spawned, they will get the last position of the player and keep moving towards that direction until they hit the stage and gets removed. However, i seem to be having a problem with the chase code. Even after reading tons of articles that offer the same chunk of code, im still unable to make it work (IM DOING IT WRONG ARRGH).
This is the main class
package
{
import flash.display.*;
import flash.events.*;
import flash.utils.*;
import flash.ui.*;
public class main extends MovieClip
{
private var left,right,up,down,fire,mouseRight,mouseLeft:Boolean;
private var speedX,speedY,mobPosX,mobPosY:int;
private var num:Number;
private var wizard:Player;
private var crosshair:Crosshair;
private var mobArray,magicArray:Array;
public function main()
{
//Hide mouse for crosshair
Mouse.hide();
crosshair = new Crosshair();
addChild(crosshair);
crosshair.x = stage.stageWidth;
crosshair.y = stage.stageHeight;
//Set initial speed
speedX = 0;
speedY = 0;
//Wizard stuff
fire = false;
wizard = new Player();
addChild(wizard);
wizard.x = stage.stageWidth / 2;
wizard.y = stage.stageHeight / 2;
//Mob stuff
mobArray = new Array();
magicArray = new Array();
//Initialize bool so movement doesn't get stuck on startup
up = false;
down = false;
left = false;
right = false;
}
public function startGame()
{
addEventListener(Event.ENTER_FRAME,update);
stage.addEventListener(KeyboardEvent.KEY_DOWN,keyDownHandler);
stage.addEventListener(KeyboardEvent.KEY_UP,keyUpHandler);
stage.addEventListener(MouseEvent.CLICK, myClick);
}
private function keyDownHandler(evt:KeyboardEvent)
{
if (evt.keyCode == 37)
{
left = true;
}
if (evt.keyCode == 38)
{
up = true;
}
if (evt.keyCode == 39)
{
right = true;
}
if (evt.keyCode == 40)
{
down = true;
}
if (evt.keyCode == 67)
{
trace(mobArray.length);
}
}
private function keyUpHandler(evt:KeyboardEvent)
{
if (evt.keyCode == 37)
{
left = false;
speedX = 0;
}
if (evt.keyCode == 38)
{
up = false;
speedY = 0;
}
if (evt.keyCode == 39)
{
right = false;
speedX = 0;
}
if (evt.keyCode == 40)
{
down = false;
speedY = 0;
}
}
function myClick(eventObject:MouseEvent)
{
fire = true;
}
public function update(evt:Event)
{
//UI
crosshair.x = mouseX;
crosshair.y = mouseY;
//Start player
if (left && right == false)
{
speedX = -8;
}
if (up && down == false)
{
speedY = -8;
}
if (down && up == false)
{
speedY = 8;
}
if (right && left == false)
{
speedX = 8;
}
wizard.x += speedX;
wizard.y += speedY;
for (var i = mobArray.length - 1; i >= 0; i--)
{
//Start mob //if X is zero and Y > 10, spawn.
var m:Zombie = new Zombie();
m.chase((Math.atan2(mobArray[i].y - wizard.y,mobArray[i].x - wizard.x)/Math.PI * 180)); //applies trigo
num = Math.random();
if (num < 0.1)
{
//when x = 0
mobPosX = 10;
mobPosY = Math.floor(Math.random() * 590) + 10;
}
else if (num < 0.3)
{
//when y = 0
mobPosX = Math.floor(Math.random() * 790) + 10;
mobPosY = 10;
}
else if (num < 0.6)
{
mobPosX = 800;
mobPosY = Math.floor(Math.random() * 590) + 10;
//when x width of screen
}
else if (num < 0.9)
{
//y is height of screen
mobPosX = Math.floor(Math.random() * 790) + 10;
mobPosY = 590;
}
m.x = mobPosX;
m.y = mobPosY;
mobArray.push(m);
addChild(m);
}
}
private function gameOver()
{
removeEventListener(Event.ENTER_FRAME,update);
stage.removeEventListener(KeyboardEvent.KEY_DOWN,keyDownHandler);
stage.removeEventListener(KeyboardEvent.KEY_UP,keyUpHandler);
}
}//end class
}//end package
This is the zombie class
package
{
import flash.display.*;
import flash.events.*;
public class Zombie extends MovieClip
{
private var zombSpd:Number;
private var angle:Number;
public function Zombie()
{
zombSpd = 10;
}
public function chase(chaseAngle:Number)
{
angle = chaseAngle;
}
public function update()
{
this.x+=Math.cos(angle*Math.PI/180)*zombSpd;
this.y+=Math.sin(angle*Math.PI/180)*zombSpd;
}
}//end class
}//end package
Thank you :)

Answer 1

I just reread your code and see that you must read and learn more about programming before trying to create a game like this.
the reason your zombies are not spawning are because you never get inside the for loop. mob array length will be zero to start with, so the for loop will never happen.
take that for loop out and create a function to spawn enemies in your main class. you can use the code you use in your for loop as the code for this function example:
function spawn():void{
//code directly from your for loop, with a small change
num = Math.random();
if (num < 0.1)
{
//when x = 0
mobPosX = 10;
mobPosY = Math.floor(Math.random() * 590) + 10;
}
else if (num < 0.3)
{
//when y = 0
mobPosX = Math.floor(Math.random() * 790) + 10;
mobPosY = 10;
}
else if (num < 0.6)
{
mobPosX = 800;
mobPosY = Math.floor(Math.random() * 590) + 10;
//when x width of screen
}
else if (num < 0.9)
{
//y is height of screen
mobPosX = Math.floor(Math.random() * 790) + 10;
mobPosY = 590;
}
var m:Zombie = new Zombie();
m.x = mobPosX;
m.y = mobPosY;
m.chase((Math.atan2(m.y - wizard.y,m.x - wizard.x)/Math.PI * 180)); //applies trigo
mobArray.push(m);
addChild(m);
}
now in your update function you must determine when you want enemies to spawn. you can do this by using a counter. Ill let you figure that part out, but if you want zombies to spawn continuously, (where your forloop in the update function was) add this:
//use a counter variable to determine when to execute spawn
spawn();
//loop through all zombies
for(var i:int = 0; i < mobArray.length; i++){
mobArray[i].update();
}

Answer 2

Steering behavior example at AdvanceEDActionScriptAnimation with abstracted interfaces and marshaling implementation.
Github:https://github.com/yangboz/as3SteeringBehavior