Le 02/11/2011 18:09, Brendan Eich a écrit :
> On Nov 2, 2011, at 4:10 AM, David Bruant wrote:
>
>> Another topic:
>> -----
>> class Monster {
>>
>> private name, health;
>>
>> sameName(other) {
>> return @name === other@name;
>> }
>> }
>> -----
>> I am under this impression that you are accessing the private property
>> ("other@name") of an instance which isn't you (other !== this) and I'm not
>> sure it's a good idea.
> Private names do not leak via reflection, not even via proxies. So what's the
> problem?
My problem is that private names are per-class instead of per-instance.
This is saying that an instance cannot isolate itself from other
instances of the same class.
It doesn't smell good to me in terms of encapsulation.
I am a human being, you are a human being. It doesn't mean we can trust
each other. If I have a password in my head, I don't want you to be able
to access it just because we are both human beings. I want my password
to be safe from foxes, cats, but also other human beings.
>> Is "other" a monster? (how do you "recognize" a monster from any other
>> object?).
> You could do ad-hoc type or shape tests. For the example, and even in most
> cases in general, there's no need. Duck typing works with private names too.
Who is "you" in your case? My "you" was "runtime". I think runtime
shouldn't do heuristic-tests like comparing shapes.
>> If so, is it a good enough reason for you to be able to access its private
>> state?
> It must be an instance of this class or the name would not be bound.
Is it a good idea that all instances of the same class can access each
others private state? I don't think this is possible in Java, I don't
know an object-oriented language where this is possible. Is there a
precedent of this? Doesn't it break encapsulation?
I think that private names should be "per-instance per-property" rather
than "per-class per-property".
"it must be an instance of this class". I'd like to ask the question
again, how does runtime knows that an object is a instance of a given
class? Will there be an internal property for this? [[Class]]? What is
the value of this internal property for objects not created with classes?
>> What happens in the following case?
>> -----
>> class Monster{
>> private health;
>>
>> constructor(health) {
>> @health = health;
>> }
>> }
>>
>> let m = new Monster(100);
>>
>> // pass m to a potentially malicious script:
>>
>> m.kill = function(){
>> @health = 0;
> health is not in scope here!
Ok, cool :-)
David
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