This is exacatly the point - you create the methods and the variable
together, so either you get a copy of all of them, or you get a new
instance.
But if you want a 'private' variable for each instance, the only way you are
going to achieve this (I think) is by creating a separate closure for each
object creation. So you can either do the above second solution, or you can
do
var obj = {
getA : function getA() {
return this.a;
},
setA : function setA(b) {
a = this.b;
}
};
function F(){ this.a = 'a';}
for (i =0; i<10;i++) x.push((function(){ F.prototype = obj; return new
F();})();
And you will still be exposing a in the end. But the point is, this is much
less readable and performance-wise I don't think it really matters, so your
second pattern is good enough IMO.
note - this list beeing so heavy on js wizards, I'm always a little afraid
of posting comments here...
On Thu, Dec 23, 2010 at 8:23 AM, Yu-Hsuan Lai <[email protected]> wrote:
> I'm trying use prototypal inheritance instead of classical one. But I'm
> still confused.
> I can't complete very very very small tasks, like this one:
> Create 10 copies of a object(with a private variant and public functions to
> access it) in an array.
>
> I have two way to approach it, first is to use Object#create:
> var x=[];
> x[0]=(function () {
> var a=10;
> return {
> getA : function getA() {
> return a;
> },
> setA : function setA(b) {
> a = b;
> }
> };
> })();
> for(var i=1; i<10; i++)
> x[i] = Object.create(x[0]);
>
> But all 10 objects' "a"s refer to a single integer. Tragedy.
> My second way is call a function which return a object 10 times:
> function createX() {
> var a=10;
> return {
> getA : function getA() {
> return a;
> },
> setA : function setA(b) {
> a = b;
> }
> };
> }
> var x=[];
> for(var i=0; i<10; i++)
> x[i] = createX();
>
> It works. But every x has its own "getA" and "setA" instance. In contrast
> to the former, it costs more memory.
> I know it maybe doesn't matter. But knowing prototypal OO can use only one
> instance, creating 10 let me regard me as a stupid.
>
> Except the two methods, the only one method I can figure out is...
> classical OO.
> Is it avoidable?
>
>
>
> --
> Lai, Yu-Hsuan
>
> --
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--
Arieh Glazer
אריה גלזר
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