Understanding Inheritance

1

Ok i’m trying to understand something here. I started off a project with a mp3 player I wanted to have one class for the sound controls and another for the drag sound position bar. So I had a bunch of properties and methods that I set up in the sound position bar class that I wanted to inherit from. So I thought after reading a bit on Inheritance its a piece of cake but yes I was mistaken or probably i’m more like stupid.

So I simplified the task a little to try and understand it all. I made an A and B class, B extends A. Here is the code and the output from it.


//class A
class com.A {
	private var p:Number;
	private var holder_mc:MovieClip;
	function A(clip:MovieClip) {
		holder_mc = clip;
		trace("Class A Constructor working and desplaying the movieclip: "+holder_mc);
	}
	public function updateP(num:Number):Void {
		p = num;
		trace("P = "+p);
	}
}



// class B
import com.A;
class com.B extends A {
	function B() {
		trace("Class B Constructor working");
		updateP(100);
		trace("trying to Inherit the path of the movieclip holder_mc from class A : "+holder_mc);
	}
}

In my FLA file I tried this


import com.*
createEmptyMovieClip("textClip", 1);
var instanceA:A = new A(textClip);
var instanceB:B = new B();

Here was my output:

A Class Constructor working and desplaying the movieclip: _level0.textClip
A Class Constructor working and desplaying the movieclip: undefined
B Class Constructor working
P = 100
trying to inherite the path of the movieclip holder_mc from class A :undefined

Ok so first off I noticed that when I made an instance from class B it also called class A Constructor again? Is this meant to happen?
If it is meant to happen then what I’m trying to do will fail.
As you can see from the output that the calling of the A Constructor a second time has set my holder_mc property to undefined.
Meaning that when I try to access this property from the B class it will be undefined instead of been able to inherit this property from A.

This is so frustrating I have read so much on this and now it’s turning my head around in circles. Can someone please set me straight and fill me in on how I could achieve what I’m trying to do.

I’m really determined to inherit this new way of action script but it’s inherently a pain in the *** for me anyway. Please help :frowning: