On Mon, Sep 15, 2014 at 2:42 PM, Allen Wirfs-Brock <[email protected]> wrote:
> > On Sep 14, 2014, at 7:47 PM, Domenic Denicola wrote: > > I want to give a +1 to Allen. The syntax really is > what-you-see-is-what-you-get, which is a great virtue. The C++-derived > initializer is cute and tempting, but not nearly as powerful or easy to > grok. > > That said, I feel weakly that requiring the correct `this = new > super(...)`and/or `this = Object.create(new^.prototype)` invocation is a > high price to pay for every derived class ever. In particular, "basic > constructor functions" (ES5 "classes") that don't wish to use the > superclass constructor don't need `this = Object.create(new^.prototype)`, > so making ES6 classes require that is strange. It feels like protypal > inheritance has "broken" once you start using ES6 classes, and it requires > you to fix it by manually doing something that was previously implicit. > > I think I'd most be in favor of a third option that implicitly adds `this > = Object.create(new^.prototype)` if no `this`-assignment is present. That > way, the superclass constructor is never implicitly called, which is kind > of what you would expect. But if you do no `this =` assignment, things > don't totally break: you still get your prototype and a valid `this`, but > you don't inherit the allocation or initialization logic from the > superclass. > > > Thanks, that's a plausible third alternative to the two variations we > already have. I'll take a look at creating a gist for that alternative. > > Since there has been a lot of talk about verboseness of `this=` I want to > compare several alternatives for a derived class that wants to do it's own > allocation: (this is derived from the last example in > https://gist.github.com/allenwb/291035fbf910eab8e9a6 ): > > If `this=` assignment is not allowed then any locally allocating method > has to look something like this: > > ```js > constructor(a) { > let newO = new^.specialAllocationMethod(); //or Object.create(new^), > etc. > newO.a = a; > return newO; > } > ``` > > with `this`` assignment it looks like: > ```js > constructor(a) { > this = new^.specialAllocationMethod(); //or Object.create(new^), etc. > this.a = a; > } > ``` > > Which is more verbose? > The first is also objectionable because it breaks existing implicit return semantics. Rick
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