Correction: The scope for ro names could be the same as for private names, except that they can be read from outside.
On Fri, Dec 13, 2013 at 8:39 PM, Andrea Giammarchi < [email protected]> wrote: > P.S. I swear I thought this was JSMentors ML ... sorry for that > > > On Fri, Dec 13, 2013 at 10:19 AM, Andrea Giammarchi < > [email protected]> wrote: > >> the closer/best option would be probably this one: >> >> ```javascript >> function Obj() { >> var xValue = 2; >> Object.defineProperties(this, { >> x: { >> enumerable: true, >> configurable: false, >> get: function x() { >> return xValue; >> }, >> set: function x(value) { >> throw 'not allowed'; >> } >> }, >> setX: { >> enumerable: true, >> configurable: false, >> writable: false, >> value: function setX(value) { >> xValue = value; >> } >> } >> }); >> } >> ``` >> >> However, this patter stinks for many reasons: >> >> 1. bad performance per each object initialization, avoid if you need >> to create many Obj instances >> 2. it's unclear why the `setX()` is better than just using the setter >> ... you have a public directly accessible property but you want a method >> to >> set its value ... you are not making its value settable only privatly, you >> are exposing the possibility so you gain nothing in terms of "security" >> >> Best Regards >> >> >> >> >> >> On Fri, Dec 13, 2013 at 8:48 AM, raul mihaila <[email protected]>wrote: >> >>> @Jeremy: something similar could be achieved with a private name (I want >>> object properties) and accessor properties, but it lacks the advantages >>> that I mentioned (also outside classes and object literals, the accessor >>> properties are ugly). >>> @Claude: that's not easy to use, and also it can be done outside the >>> execution context. >>> >>> >>> On Fri, Dec 13, 2013 at 6:20 PM, Claude Pache <[email protected]>wrote: >>> >>>> >>>> If you are not paranoid, you can just use nonwritable properties. That >>>> forces you to use `Object.defineProperty` to change the value, so you are >>>> protected against accidental assignments. >>>> >>>> function Obj() { >>>> Object.defineProperty(this, 'x', { value: 2, writable: false, >>>> enumerable: true, configurable: true }) >>>> this.setX = function (val) { >>>> Object.defineProperty(this, 'x', { value: val }) >>>> } >>>> } >>>> >>>> o = new Obj >>>> o.x = 17 // assignment will fail; moreover, in strict mode, an >>>> error is thrown >>>> o.x // 2 >>>> o.setX(18) >>>> o.x // 18 >>>> >>>> It doesn't prevent the user from hanging themself with >>>> `Object.defineProperty(o, 'x', { value: 17 })`; but at least, it won't be >>>> by chance! >>>> >>>> —Claude >>>> >>>> >>>> Le 13 déc. 2013 à 14:34, raul mihaila <[email protected]> a écrit >>>> : >>>> >>>> Hello, was there any proposal for object properties that can be read >>>> from anywhere but are writable only from the execution context where the >>>> name associated with the property was defined? Something like: >>>> >>>> function Obj() { >>>> ro x; // read only name x >>>> this.x = 2; >>>> this.setX = function (val) { >>>> this.x = val; >>>> }; >>>> } >>>> >>>> var o = new Obj; >>>> >>>> o.x; // 2 >>>> o.x = 43; // throws some error >>>> o.x; // 2 >>>> o.setX(100); >>>> o.x; // 100 >>>> >>>> The advantages would be that you are sure that there are no side >>>> effects when the property is accessed and also I'm guessing you have no >>>> function call overhead. >>>> _______________________________________________ >>>> es-discuss mailing list >>>> [email protected] >>>> https://mail.mozilla.org/listinfo/es-discuss >>>> >>>> >>>> >>> >>> _______________________________________________ >>> es-discuss mailing list >>> [email protected] >>> https://mail.mozilla.org/listinfo/es-discuss >>> >>> >> >
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