base.js with sandboxing

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I'm using an implementation of base.js from here: http://ejohn.org/blog/simple-javascript-inheritance/

I attempted to combine this with sandboxing to get "private" variables. For example:

JavaScript

// Sandbox.
(function () {

var privateVar;

myClass = Class.extend({
    init: function (bindingOptions) {
        privateVar = 0;
    },

getPrivateVar: function() {
    return privateVar;
},

setPrivateVar: function(value) {
    privateVar = value;
});
})();

However, when I try to make 2 instances, of course the "privateVar" has the same value. For example:

JavaScript

var class1 = new myClass();
var class2 = new myClass();
class1.setPrivateVar(5); // now both class1 and class2 report privateVar as "5"

Is there any way to get private variables using this methodology that are scoped to the object without resorting to "this._privateField" ?

Posted 24-Jan-13 8:24am

Terrence Sheflin

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2 solutions

Solution 1

If you want instance specific private variables,

JavaScript

function ClassConstructor(...) {
var that = this;
var membername = value;
function privatememthod(...) {...}

}

you have instance specific private variable membername & private method privatemethod.

Access for external methods:

JavaScript

function ClassConstructor(...) {
var that = this;
var membername = value;
function privatememthod(...) {...}

return {
  getPrivareMember: function(){
       return membername;
  }
}
}

Posted 24-Jan-13 8:42am

Vyacheslav Voronenko

Updated 24-Jan-13 8:45am

v2

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Terrence Sheflin · Accepted Answer · 2013-01-24T09:06:00

After further research, the answer here is that it isn't possible.

Reference: http://robertnyman.com/2008/10/21/javascript-inheritance-experimenting-with-syntax-alternatives-and-private-variables/[^]

The reason is that if you use the sandboxing methodology I outlined above, any "private" variable declared will be static. Methods, however, can successfully be hidden and work.