Polymorphism and deep inheritance in JS

I'm using the JS prototype inheritance pattern from Gavin Kistner and I'm not quite sure why deep inheritance doesn't work for me.

I want C inherits from B inherits from A...

Function.prototype.inheritsFrom = function( parentClassOrObject )
{
   if ( parentClassOrObject.constructor == Function )
   {
      //Normal Inheritance
      this.prototype = new parentClassOrObject;
      this.prototype.constructor = this;
      this.prototype.parent = parentClassOrObject.prototype;
   }
   else
   {
      //Pure Virtual Inheritance
      this.prototype = parentClassOrObject;
      this.prototype.constructor = this;
      this.prototype.parent = parentClassOrObject;
   }
   return this;
}

function A() {
   // ...
}
A.prototype.init = function( arg ) {
   // ...
}

function B() {
   A.apply( this, arguments );  // call super constructor
   // ...
}
B.inheritsFrom( A );
B.prototype.init = function( arg ) {
    B.parent.init.call( this, arg );
    // ...
}

function C() {
   B.apply( this, arguments ); // call super constructor
   // ...
}
C.inheritsFrom( B );
C.prototype.init = function( arg ) {
   this.parent.init.call( this, arg );
   // ...
}

var foo = new C();
foo.init( 10 );  

// Throws an exception: infinite call loop.

When I call foo.init(), I'm actually calling C.init()

Inside C.init() 'this' is of type C

-> this.parent.init.call( this, arg ) is actually calling B.init()

Inside B.init() 'this' is still of type C ( because of .call(this))

-> this.parent.init.call( this, arg ) is, again, calling B.init() 开发者_如何转开发

And therefore it goes into an infinite call loop on B.init() ...

What am I doing wrong ?

Should I simply rename 'init' to something else for B and C ? I would rather not, because the current way allows me to call obj.init() whether obj is of type A, B or C...

Change B.parent.init.call( this, arg ); to B.prototype.parent.init.call( this, arg );.

This doesn't answer your question, but I have been doing some work with JavaScript inheritance recently. If you want to go the classical route, I can really recommend JS.Class; it's a library that makes classes really easy.

If you can, you should avoid using the library, but if you don't want to deal with the headache of JavaScript inheritance/prototyping, I can recommend JS.Class.