[AS3] Space Invaders + classes

[Geoff666]

Hi there,

I'm kinda new to AS3 and doing my very best to learn the basics.
I'm familiar with AS2, so syntax isn't really a problem.

For learning AS3 I decided to make some sort of Space Invaders, this because it involves classes, and that's the problem I bump in now.

From a tutorial I've been told classes are written like this;


package {
import flash.display.MovieClip;
public class Alien1 extends MovieClip
{
public function InitEnemy()
{
x=100;
y=100;
}

public function MoveEnemy()
{
y++;
}
}
}

I've linked the alien sprite to that class, but still it isnt being initialized when I test the movie.
I've been using 2 files btw, 1 for the sprite (.fla), and 1 for the class (.as), and so far, my .fla doesnt contain any code.

Am I doing this the right way, or did I forget something really stupid?
Any help would be much appreciated!


Thanks in advance,

Geoff.

[kingundkong]

name your constructor class the same as you class, so this gets fired when you construct your alien. your class should look like:

package
{
import flash.display.MovieClip;
public class Alien extends MovieClip
{
public function Alien()
{
x = 100;
y = 100;
}

public function MoveEnemy()
{
y++;
}
}
}

link your graphical alien in the library to the class Alien and
on the main timeline write:

var alien:MovieClip= new Alien();
this.addChild(alien);

hope this helps.

[Geoff666]

I've tried your solution, but it still doesn't work.
I probably did something wrong with the "var alien:MovieClip= new Alien();
this.addChild(alien);"-part.

With 'main timeline' you mean the first frame of my .fla timeline, right?

[rrh]

Do you have set "export on first frame" in the library properties of the Alien?

[Geoff666]

Yeah, I did. :eek:

[kingundkong]

did you name your class Alien not Alien1 in your classfile?

[Geoff666]

I assume you mean my .as file?

I'll post it, might save us a few hundred posts :p

-------------.as-file:------------------

package {
import flash.display.MovieClip;
public class Alien1 extends MovieClip
{
public function Alien1()
{
x=100;
y=100;
}

public function MoveEnemy()
{
y++;
}
}
}

-----------.fla-file-------------------

var alien:MovieClip= new Alien1();
this.addChild(alien);



For the rest I've been to library -> alien-object -> linked it to "Alien1"
And set the import to first frame thingy.

I really can't seem to spot the problem.

[kingundkong]

your class should look like this:

package
{
import flash.display.MovieClip;
public class Alien extends MovieClip
{
public function Alien()
{
x = 100;
y = 100;
}

public function MoveEnemy()
{
y++;
}
}
}

[Geoff666]

That still does not do the trick :(

[kingundkong]

i attached a sample fla+as file, just take a look. i guess you did not name your cymbal in the library the right way or did not link it in the right way to the class file.

[Geoff666]

I can't open the .fla file, Flash crashes and tells me to report -.-'
Are you using CS4?

Could you maybe explain to me how to properly link a sprite to a object?
Thanks in advance!

[kingundkong]

ups, yeah its cs4, so here is the cs3 verison.

[Geoff666]

Can't open it either.
But I see you're haveing a Mac, and I'm still on sucky WXP, would that make a difference?

[rrh]

What is it doing instead of working?

Is it not visually appearing on the stage, or is it appearing but not following the behaviour defined in the code, or what?

[kingundkong]

this should not be a problem. what is your error message

[Geoff666]

It says it encountered unexpected file content, and shuts down whenever i close the report.

@ rrh
In my .fla i've set the graphical object on my screen, and thats exactly what it shows.
It doesnt set ts x,y on 100.
So I guess the object isn;t listening to the code.

[kingundkong]

you do not need to put the graphical object on stage. by doing
var alien:MovieClip= new Alien();
this.addChild(alien);
you put it on stage and than it will be at x, y position you were setting in the as file

[Geoff666]

OK! Got it working now.. or atleast the initialization, it doesn't move, while it should.

EDIT: wait, i'm thinking too hard.
I need to call it;s movement function, right?
where do i do that?

[kingundkong]

for having it move you need to set a timer or an enter frame event and call the alien.MoveEnemy() function;

[Geoff666]

in the main timeline that is?

[Geoff666]

Ok, got that working too, thanks all!!


Now my I have another question..
When you object oriented programming, is this the right way to do it then?

I added a eventlistener in the main timeline which calls all functions.