Le 25/09/2013 17:59, Allen Wirfs-Brock a écrit :
On Sep 25, 2013, at 3:01 AM, David Bruant wrote:
I think it's important to have a generic solution to avoid having
magic (non-self-hostable) built-ins (but I don't have this solution).
I don't think there is one, based upon Direct Proxies.
There probably is one. Something like for a given class, register a
bunch of functions (typically the ones on the prototype) which receive
the unwrapped target if this target was the output of the class
constructor. It could look like something like (self-hosting Date):
// don't worry too much about the syntax
class Date(){
constructor(){
this.datetime = readDatetimeFromSystem();
setInterval(()=>{ this.datetime++; }, 1);
}
private datetime;
public getMonth(){
return someComputation(this.datetime);
}
}
// only the class creator should be able to do that (maybe "class"
should be an expression returning the capability or something)
Date.functionsWhereThisShouldBeUnwrapped = [Date.prototype.getMonth];
var d = new Date();
var p = new Proxy(d, {});
d.getMonth(); // works
// the method sees c because 1) it's "whitelisted", 2) the target
is a Date instance
var p2 = new Proxy({}, {}); // random target
p2.getMonth = p.getMonth;
p2.getMonth(); // throws because p2 wasn't created by the Date
constructor and the private state can't be found
Edges are a bit hand-wavy, but I hope you get my point that in a way or
another, it's possible to maintain the information of which constructor
created what function and tell with fine-grain which function should
unwrap automatically to the target (leading to private state access).
That's why if we want to have Proxy as a primitive that supports
creating membranes we need to stop thinking about it as a more
universal primitive that also supports things like transparent forwarding
Why would the 2 goals be contradictory?
David
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