On Tue, Jul 19, 2011 at 11:23 AM, Brendan Eich <[email protected]> wrote:
> On Jul 19, 2011, at 11:07 AM, Bob Nystrom wrote: > > // "new" lets you declare members on new instances. these would presumably > be > > // invoked on the new object before the constructor body is run. > new: > numAttacks = 0; > // declaring an instance property here mainly so you can document it. > could be > // useful later for guards or other annotations. > name; > > > The plain name; also looks like a useless expression-statement. > Yeah. :( Granted, it isn't even necessary so this corner case may not matter much. I mentioned it because our earlier proposals have included a declarative syntax for instance properties, even though it's mostly for documentation. > Beyond this, I'm concerned that per-instance properties need initializers > that use constructor parameters. So they ought to be initialized in the > constructor. > Agreed. The ctor is where the real magic happens. Declaring instance properties at the class level is just bonus. It would be useful for things like having a place to hang a Closure-style type annotation comment, but wouldn't be critical at runtime. Whether they can be declared outside the constructor is a separate issue. > Perhaps if they have constant or constructor-invariant initializers, they > can be initialized where declared too. > Exactly. I do like the ability to declare and initialize per-instance properties outside the constructor for properties that *don't* depend on constructor arguments since it highlights that fact, but it isn't a key requirement. > But declarations should look different from expressions. The alternative we > keep returning to is the property assignment sub-grammar of object literals, > which would want > > new: > numAttacks: 0; > I'd worry that that's too close to the prototype: and class: section syntax we're talking about adding. We use ":" so much already that I hesitate to invoke it again. - bob
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