[swift-evolution] #available has a huge anti-pattern.

[James Campbell]

Awesome :)

*___________________________________*

*James⎥Lead Engineer*

*james at supmenow.com <james at supmenow.com>⎥supmenow.com <http://supmenow.com>*

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On Tue, Feb 2, 2016 at 4:26 PM, Joe Groff <jgroff at apple.com> wrote:

> Polyfills have their own tradeoffs; they tend to encourage constant
> accretion of glue code as new versions get added if there's no pressure to
> drop old versions, leading to a significant amount of the multi-megabyte
> Javascript framework downloads we all complain about these days. That said,
> you might be able to use the related `@available` attribute to introduce
> backfill extensions that are only available on older systems.
>
> -Joe
>
> On Feb 2, 2016, at 2:03 AM, James Campbell via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> Coming from a web background (before my iOS career) to me #avaliable has
> huge problem. It encourages fragility.
>
> In my eyes we should encourage two types of detection: Features to make
> code more adaptable to different environments and language version
> detection: so we can understand the actual code.
>
> See this example below:
>
> func magic(object: Object)
> {
>   if(#avaliable(9.0, 10))
>  {
>   object.foo()
>  }
> }
>
> Ideally for me I would love to check if the foo function exists like so:
>
> func iOS9OnlyProtocolFunction(object: Object)
> {
>   if(#avaliable(Object.foo))
>  {
>     object.foo()
>  }
> else
> {
>   object.baz()
>  }
> }
>
> I think this encourages feature detection which results in less fragile
> code. What I would love to do is also to extend this to extensions so we
> could encourage polyfills.
>
> extend object where not_avaliable(Object.foo)
> {
>   func foo()
>  {
>    //Polyfill for platforms which don't support the Object.foo method
>  }
> }
>
> Not sure about compiler details but being able to polyfill the function
> results in much cleaner code for me. I love this approach from the web, so
> I created my own Objective-C Library to do this:
>
> https://github.com/jcampbell05/Polly
>
> *___________________________________*
>
> *James⎥Lead Engineer*
>
> *james at supmenow.com <james at supmenow.com>⎥supmenow.com
> <http://supmenow.com/>*
>
> *Sup*
>
> *Runway East *
>
> *10 Finsbury Square*
>
> *London*
>
> * EC2A 1AF *
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