Question

I want to call setter “transform” in the superclass SceneNode from the overriden setter in the subclass Camera.

The classes look like this:

SceneNode:

function SceneNode(){
    this._transform = M4x4.I;
}

SceneNode.prototype.__defineSetter__("transform", 
    function(transform){
        this._transform = transform;
    }       
);

SceneNode.prototype.__defineGetter__("transform", 
    function(){
        return this._transform;
    }   
);

Camera:

function Camera(){

}

Camera.prototype = new SceneNode();
Camera.base = SceneNode.prototype;

Camera.prototype.__defineSetter__("transform",
    function(transform){
        Camera.base.transform.call(this, transform);
        this.updateViewMatrix();
    }       
);

Camera.prototype.__defineGetter__("transform", 
    function(){
        return this._transform;
    }   
);

This does not work because “Camera.base.transform” is not defined according to firefox. I used to call “Camera.base.setTransform.call(this, transform);” before, which worked, but since I learned about setters and getters, I tried to get rid of setXXX functions.

Answer 1

Getters and setters hide the underlying function, so you need a way to bypass the property and obtain the setter directly. (It’s undefined because it’s actually accessing the return value of SceneNode.prototype‘s getter, which has no instance to get a value from.) The counterpart to __defineSetter__ is __lookupSetter__:

Camera.prototype.__defineSetter__("transform",
    function(transform){
        Camera.base.__lookupSetter__("transform").call(this, transform);
        this.updateViewMatrix();
    }
);

But those methods are deprecated, so the correct (ECMAScript 5) way is to use Object.defineProperty and Object.getOwnPropertyDescriptor:

Object.defineProperty(Camera.prototype, 'transform', {
    set: function(transform){
        Object.getOwnPropertyDescriptor(Camera.base, 'transform').set.call(this,
                transform);
        this.updateViewMatrix();
    },

    get: function(){
        return this._transform;
    }
});