undefined | Better HN

0 pointswwweston11y ago0 comments

> with Proxy you don't have to write the functions any more, you could just define that one get on the handler you feed into Proxy

Doable with "old" JS. Consider this function:

    function prop(name, gNs) {
        var _name = '_' + name, 
	    get = gNs && gNs.get, 
	    set = gNs && gNs.set, 
	    undef = function (v) { return typeof v == 'undefined'; },

        if (get && set)
            return function (x) { return undef(x) ? get.call(this, this[_name]) : (this[_name] = set.call(this, x), this); }

        if (get && !set)
            return function (x) { return undef(x) ? get.call(this, this[_name]) : (this[_name] = x, this); }

        if (!get && set)
            return function (x) { return undef(x) ? this[_name] : (this[_name] = set.call(this, x), this); }

        return function (x) { return undef(x) ? this[_name] : (this[_name] = x, this); }
    }

Pass `prop` (a) the name of a property you're defining getter/setter methods for and (b) an object with any custom getter/setter you might care to define (or neither, if you like), and it'll return a function that will act as both which you can assign to a prototype.

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3 comments · 1 top-level

btipling11y ago· 2 in thread

I like that, but you'd still have to call a function to get the properties though and this wouldn't prevent anyone from accessing those properties directly.

Like:

  obj.setFoo("bar");
  obj.getFoo();
  obj.foo = "bad stuff"; //overwritten

instead of

  obj.foo = "bar";
  obj.foo;
  obj.foo_ //error, not allowed access

wwwestonOP11y ago

True enough, and if privacy is a must have, my implementation is a non-starter.

I tend towards the (somewhat unpopular and certain arguable) opinion that need for privacy via a runtime-enforced mechanism is overrated... give us developers using an API/library effective/well-documented methods that do what we need and warn us when we shouldn't touch something with a convention (like an underscore), and usually we're happy to leave the black box closed.

It's usually when abstractions leak or implementations aren't complete that we're tempted to tinker across boundaries, and when that happens, the lack of a privacy enforcement mechanism may not be the real problem.

(OTOH, they can indeed help keep some bad situations from getting worse, and when trusted code is mingling with untrusted in situations like web mashups, privacy-enforcement can be really helpful for security...)

btipling11y ago

I don't know why, because I haven't thought through it enough yet but I really like the idea of freezing or protection in the case of a reactive data model like Backbone models. I'm thinking of maybe writing up some quick implementation where you provide a schema and you get a reactive object that is frozen and has a catch all. Just want to see where that goes.

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