It won't work.
In JavaScript, the prototype based inheritance is only property inheritance.
It does not extend to internal fields, like [[Class]] or internal values of,
e.g., Date, Number, String, or Boolean.
You will have the exact same behavior if you try to inherit from, e.g.,
Date.
The internal time value of a Date object belongs to the Date object only, it
is not inherited along the prototype chain.
That means that an object created using:
function Foo(){};
Foo.prototype = new Date();
var foo = new Foo;
does not function as a Date object - it's internal [[Class]] property isn't
"Date" and the Date specific functions will throw exceptions if called,
e.g.:
print(Object.prototype.toString.call(foo)); // prints [object Object],
not [object Date].
print(foo.getTime()); // throws "TypeError: this is not a Date object."
My guess at the problem of test 3 is that you are using the Base
constructor on an object that isn't created from the Base object
template. That means that the object doesn't have an internal field slot 0
(or if it has, it's being used for something else), and you are just reading
and writing some other field of the object that is later overwritten again,
possibly by the foo property. The same happens in test 2, but the field just
happens not to be overwritten before it's read.
(I.e., the code is unsafe, since it assumes an internal field count, but
doesn't check that the object is created from the correct template).
Best of luck.
/L
2010/3/17 Henrik Lindqvist <henrik.lindqv...@gmail.com>
> "IIRC, this isn't the way to do it in v8"
>
> I don't want to force users to do it the V8 way, I want them to do it
> the JavaScript way.
>
> You write in your derived constructor:
> function MyPanel() {
> var argv = Array.prototype.slice.apply(arguments,[0]);
> this.prototype = this.__proto__ = new ncurses.NCPanel(argv);
> // ...
> return this;
> }
>
> What is the property this.prototype?
> In the constructor, isn't "this" the instance, then it has no
> "prototype" property, that is on the constructor (function).
> I don't see why I should use the "__proto__" property to change the
> prototype chain after the instance was created, the prototype chain
> has already been specified.
>
>
> On Mar 17, 11:38 am, Stephan Beal <sgb...@googlemail.com> wrote:
> > On Wed, Mar 17, 2010 at 2:44 AM, Henrik Lindqvist <
> >
> > henrik.lindqv...@gmail.com> wrote:
> > > "Derived2.prototype = new Base; \n"
> > > "Derived2.prototype.constructor = Derived2; \n"
> >
> > IIRC, this isn't the way to do it in v8. i remember going through similar
> > pain when i wrote my ncurses wrappper for v8, and now i find that i
> > documented it:
> >
> > http://code.google.com/p/v8-juice/wiki/PluginNCurses
> >
> > see the section called "Inheritance...", near the end of the table of
> > contents.
> >
> > i hope that helps.
> >
> > --
> > ----- stephan bealhttp://wanderinghorse.net/home/stephan/
>
> --
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> v8-users@googlegroups.com
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>
--
Lasse R.H. Nielsen
l...@google.com
'Faith without judgement merely degrades the spirit divine'
Google Denmark ApS - Frederiksborggade 20B, 1 sal - 1360 København K -
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