Multiple inheritance with node.js utils.inherits?

Question

Hi I'm new to node and I'm trying to build an MVC app. For the controllers and models I was able to use utils.inherits to create base and sub-classes. For views, I'd like to create 3 levels: base, html/json, module. At each level there is a function called construct that needs to be called when an instance is created, and calling it at the top should chain back through each level.

Base view:

function Base_view( ) {
    this._response = null;
};

Base_view.prototype.construct = function( res ) {
    this._response = res;
};

Html view:

var util = require( 'util' ),
    Base_view = require( './view' );

function Html_view( ) {
    Base_view.apply( this, arguments );
}

util.inherits( Html_view, Base_view );

Html_view.prototype.construct = function( res, name ) {
    this.constructor.super_.prototype.construct.apply( this, arguments );
};

Module view:

var util = require( 'util' ),
    Html_view = require( './../base/html' );

function Main_view( ) {
    Html_view.apply( this, arguments );
}

util.inherits( Main_view, Html_view );

Main_view.prototype.construct = function( ) {
    this.constructor.super_.prototype.construct.apply( this, arguments );
};

This line in the module view produces an undefined error:

this.constructor.super_.prototype.construct.apply( this, arguments );

If I only subclass once it correctly calls the parent classes construct method. How do I use it to extend multiple times?

In this post: util.inherits - alternative or workaround there is a modified utils.inherits method that looks like its supposed to do it but I can't figure out how to use it? I've tried requiring both classes in module and putting all three as params.

Thanks!

Generally you call your parent prototype function explicitly. So in Main_view.construct I would do Html_view.prototype.construct.apply() and then in Html_view do Base_view.prototype.construct.apply(). Explicitly call your parent's method. Of course, you are supposed to be using the function that defines the object as the constructor, not a separate method. — Chad
– Chad, Commented Sep 19, 2013 at 17:24

Jonathan · Accepted Answer · 2013-09-19 17:21:08Z

6

Got it working by removing my attempt at adding a faux callable constructor and using the func def as the constructor. Ignore the util require, it's just a wrapper to include some standard util functions and a few of my own. All it does is call the built in method.

/controllers/base/view.js:

function Base_view( res ) {
    this._response = res;
};

/controllers/base/html.js:

var util = require( '../../helpers/util' ),
    Base_view = require( './view' );

function Html_view( res, name ) {
    Base_view.apply( this, arguments );
    this._name = name;
};

util.inherits( Html_view, Base_view );

/controllers/main/html.js:

var util = require( '../../helpers/util' ),
    Html_view = require( './../base/html' );

function Main_view( res, name ) {
    Html_view.apply( this, arguments );
};

util.inherits( Main_view, Html_view );

edited Sep 19, 2013 at 17:21

answered Sep 19, 2013 at 15:49

Jonathan

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