static/class properties
Dmitry Soshnikov
dmitry.soshnikov at gmail.com
Thu Sep 19 21:20:59 PDT 2013
On Sep 19, 2013, at 6:30 AM, Rick Waldron wrote:
> On Thu, Sep 19, 2013 at 4:16 AM, Dmitry Soshnikov <dmitry.soshnikov at gmail.com> wrote:
> Hi,
>
> Out of curiosity: we have static methods, but seems there is no yet ability to define a class/static property/constant.
>
> class A {
> const VALUE = 10;
> }
>
> or (probably better to be consistent with static methods):
>
> class A {
> static VALUE = 10;
> }
>
>
>
> A decision would have to be made for "const VALUE = 10" here: does it mean mean `A.VALUE` and not `var a = new A(); a.VALUE;`?
Yes, it's true, that if a property is placed in the prototype, it can be treated sort of a "static", i.e. shared between all instances. However, I'd assume static foo = 10; means the same as static foo() {}, that is -- placed on the class object itself.
> If it means the latter, then there are implications that will change a possible future that includes "private x = 1" in the same class-body position.
>
In contrast, "private" modifier should declare a property per instance of course.
> I spoke with Allen off-line and he reminded me that a static "const-like" could be created like this:
>
> class A {
> static get VALUE() { return "some constant value"; }
> }
>
Yeah, but this is "too unsugared" for simple class consts. For accessor consts still work though.
So, if it's not that hard to add to the spec, I'd argue for:
class A {
static foo = 10; // or const foo = 10; whatever
}
desugars to:
A.foo = 10;
>
>
> function getHeavyValue() {
> static heavyValue;
> if (!heavyValue) {
> // heavy calc
> }
> return heavyValue;
> }
>
>
> This is a no-go because "static" is only reserved in strict mode, which means
>
> function foo() {
> static = 1;
> }
>
OK.
Dmitry
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