使用Google Closure进行多级继承

Question

I want to implement multiple inheritance using google closure . I have already researched and I found this book . At page 158, they say that google closure doesn't support multiple inheritance, but that there are other ways to do it, like using "goog.mixin". I tried it but I get "Uncaught AssertionError: Failure".

Basically, I want to do something like this:

class A {
    function moveLeft() {
        ...
    },
    function moveRight() {
        ...
    }
}

class B extends A {
    function moveTop() {
        ...
    }
}

class C extends B {
    function moveBottom() {
        ...
    }
}

• Class A has the methods "moveLeft" and "moveRight".
• Class B has the methods "moveLeft", "moveRight" AND "moveTop" (normal inheritance, gets the methods from the parent class A)
• Class C should have the methods "moveLeft", "moveRight", "moveTop" AND "moveBottom" (double inheritance, gets the methods from the parent class B, and the grandparent class A)

BUT class C only gets the methods of class B the way I am doing.

How could I do this using google closure?

Thank you.

João

---

EDIT 1

I will try to make myself clearer. I can't display here the whole code for professional reasons. This is a bit how my classes look like.

// external file xgis.js

xgis = {};


// xgis.map
xgis.map = function(options) {
    // map definitions ...
};
// Inherits from ol.Map
goog.inherits(xgis.map, ol.Map);


// xgis.layer
xgis.layer = function(options) {
    // base layer definitions
};


// xgis.layer.osm
xgis.layer.osm = function(options) {
    goog.base(this, {
        source: new ol.source.OSM()
    });
    sigga.layer.call(this, options);
};
// Inherits from ol.layer.Tile
goog.inherits(xgis.layer.osm, ol.layer.Tile);
/**
 * Copies all the members of a source object to a target object.
 * i.e, inherits ALSO from xgis.layer (the base layer class)
 */
goog.mixin(xgis.layer.osm.prototype, xgis.layer.prototype);

The goal is to build an SDK, which I named here "xgis". We want to build our API on top of OpenLayers 3 (ol3). We want our own methods to use the ol3 methods. We need to have our own method for documenting.

For example, I want my own method to check the visibility of a layer. But this method has to use the one from ol3 "with the same name as mine":

// My method
xgis.layer.prototype.getVisible = function() {
    // Used the method of the parent class from ol3
    return this.superClass_.getVisible();
};

I tried to use the keyword "superClass_" to get the method of the parent class, but it didn't work.

Is there another way?

Answer 1

Can you write your example as valid JavaScript? As far as I can tell this isn't "multiple inheritance" but simply multiple levels of inheritance.

I think you mean:

function A() {}
A.prototype.moveLeft = function() {};

function B() {}
goog.inherits(B, A);
A.prototype.moveTop = function() {};

function C() {}
goog.inherits(C, B);
A.prototype.moveBottom = function() {};