I actually really like the idea of using ‘async' to start a computation in a
non-blocking way. It is extremely common in real-world code to want to start a
few computations/downloads at once in the background and then use the results
together...
I think full-fledged futures could be a framework thing added on top, but what
I would really love to see at the language level is that using ‘async’ just
allows you to defer calling ‘await’. That is, you could get a value back from
something called with async, but you would be forced to await that value before
it could be used:
var image = async downloadImage() //Image is type UIImage
//Do something else here
let size = await image.size //The compiler forces me to call await
before I can actually use the value
This looks somewhat similar to a future, but you can’t interact with it as a
separate type of object. The value above is just a UIImage, but with a
compiler flag/annotation that forces me to call await on it before it can be
accessed/used. The compiler has a lot more freedom to optimize/reorganize
things behind the scenes, because it doesn’t necessarily need to make an
intermediate object.
I don’t think this is just sugar. It adds expressivity and control for a set
of very common use-cases which aren’t fully supported by await alone.
Thanks,
Jon
> On Aug 24, 2017, at 4:40 AM, Trevör ANNE DENISE via swift-evolution
> <[email protected]> wrote:
>
> Hello Swift community,
>
> I was really interested by the recent Task-based concurrency manifesto and
> Concrete proposal for async semantics in Swift.
>
> Looking at beginAsync() and Futures, I had an idea for a new syntax based on
> the `async` keyword, I'd love to hear your feedback about this idea:
> https://github.com/adtrevor/Swift-ideas/blob/master/New%20async%20keyword%20usage.md
>
> <https://github.com/adtrevor/Swift-ideas/blob/master/New%20async%20keyword%20usage.md>
>
> Would such a syntax make any sense?
>
> Thank you ! :)
>
>
> Trevör
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