On Fri, Jul 8, 2011 at 11:15 AM, Mark S. Miller <[email protected]> wrote:
> On Fri, Jul 8, 2011 at 6:36 AM, Juan Ignacio Dopazo <[email protected] > > wrote: > >> Private instance properties were considered to be accessible by all >> instances of the class. That's a new concept in ES. Were there arguments for >> keeping instance private properties private to the instance? >> > > Yes. That's done quite well by lexical capture of the constructor lexical > context by per-instance methods: > > class Point { > constructor(x, y) { > public getX() { return x; } > ... > } > } > > which basically sugars the objects-as-closure pattern. If you don't mind > the allocation cost, this is superior in almost all ways to the conventional > prototype/this-based pattern. > > "private" is needed when combining inherited methods with encapsulation. > Since inherited methods may apply to any instance of the class and are not > automagically bound to any one instance, their access to encapsulated state > cannot be any finer than per-class. > But when the number of methods that need access to the private property rises, this becomes a mess of a constructor. And it also breaks the use of super, doesn't it? My first thought was: why not just statically replace this.x, with private x, with this[xPrivateName] and forget about accessing private properties of other objects? That would still leave the problem of closures inside methods, though... Juan
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