On Dec 22, 2010, at 7:10 AM, Peter van der Zee wrote:
> What about adding an attribute to properties that somehow identify which
> classes (in the prototype chain for protected) have access to the object?
> I'll leave the "somehow" up in the air, but you could introduce a [[Private]]
> attribute which, if not undefined, says which context must be set (and for
> protected, either directly or through the prototypal chain of the current
> context) to gain access to this property. And if that context is not found,
> some error is thrown. Maybe it would be [[EncapsulationType]] :: {private,
> protected, public} and [[EncapsulationContext]] :: <?>. You could also add a
> simple api to check for these (isPrivate, isProtected, isPublic,
> hasEncapsulatedProperty, etc) depending on how it would affect "in" and
> enumeration.
IMO, this is too class-oriented for JS. We should allow the creation of private
members of arbitrary objects, not just those that inherit from new
constructors. I think it also doesn't address the use case of adding new
operations to existing classes like Object or Array without danger of name
conflicts.
> Pro's:
> - meaning of private will be more to what people expect
I find this a little hard to believe. It's tricky to make claims about what
people will expect. It's true this feels somewhat analogous to Java, but
there's a wide diversity of JS programmers. And a lot of them don't want us to
just "make it like Java" and do their best to remind us of this fairly
regularly. ;)
> - minimal "magic" going on, trying to access a private property out of scope
> should result in a proper error
> - possibly less impact on the spec (although I'm not sure there...)
> - no need to introduce a new type/class to denote private properties
This last point confuses me -- it sounds like you *have* to introduce a class
to denote private properties, because they're associated with a class. Or are
you referring to the SoftField type?
Dave
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