The book is great, so thanks for all of your hard work. I am trying to create a football game but am having difficulty with the z-axis. Could this be adjusted to include a z-axis or am I better off using a completely different method?

Many thanks

Shaun

Thanks again

Bob

So, we introduced syntax and extreme changes (events and display list) in the timeline and then introduced classes in Chapter 6. From that point on, classes will become a bigger part of your workflow. Syntax will still be introduced in isolated snippets of timeline code, so you can concentrate on the subject at hand. Then classes will be used for additional examples.

In your case, the reason you need to use this instead of ball is because you’re making references while inside the class. The first snippet in your comment creates an instance of the class in the timeline. In THAT script, you’ll use ball to refer to the ball. Inside the class, however, the code allows the ball to behave autonomously by referring to itself. If you used the reference ball, the class wouldn’t understand because ball isn’t defined anywhere that the class knows about.

Using ball inside the class would be like referring to yourself in the third person instead of using the pronoun “me.” You can control your own behavior by updating your own x and y. Your parent can create you by saying “new”, and they can direct you by name.x. If you said name.x, however, someone else would have to be in the room with you and have the same name to get any result.

Looking over your class, ask yourself where ball is defined. The answer is, nowhere. Instead, it’s defined in the timeline, where the very instance your analyzing was created. There are two scopes: timeline and class, and you have to know what you’re referring to.

I hope this makes sense.

This is on frame one of the fla

var ball:MovieClip = new Ball();
addChild(ball);

and this is what I created as Ball.as

//Ball.as
package {

   import flash.display.MovieClip;
   import flash.events.*;

   public class Ball extends MovieClip{

      public var xVel:Number = 4;
      public var yVel:Number = 4;
      public var xAcc:Number = 1;
      public var yAcc:Number = 1;

      public function Ball() {
         this.x = this.y = 100;
         addEventListener(Event.ENTER_FRAME, onLoop, false, 0, true);
      }

      function onLoop(evt:Event):void {
         this.x  = xVel;
         this.y  = yVel;

         xVel  = xAcc;
         yVel  = yAcc;
      }
   }
}

what I do not understand is why I had to change ball.x within the onLoop function to this.x in order to make it work. I would appreciate your comments.

Thank You