[swift-evolution] Switch on an optional enum -- `case: nil`?

[Ross O'Brien]

I was about to provide this, but Krzysztof's example is more compact than
mine:

enum Coin {

case heads

case tails

}

var result: Coin?


switch result {

case .Some(.heads): print("heads")

case .Some(.tails): print("tails")

case nil: print("not yet flipped") // exhaustive

}



On Thu, May 5, 2016 at 4:52 PM, Krzysztof Siejkowski via swift-evolution <
swift-evolution at swift.org> wrote:

> It doesn’t compile because you’re switching on the Optional and trying to
> pattern match it to Coin.
>
> It compiles right when you pattern match it to Optional<Coin>:
>
> switch result {
>
> case .heads?: print("heads")
>
> case .tails?: print("tails")
>
> case nil: print("not yet flipped")
>
> }
>
> Best,
> Krzysztof
>
>
> On 5 May 2016 at 17:42:24, Eric Miller via swift-evolution (
> swift-evolution at swift.org) wrote:
>
> Wondering if you guys think this is a reasonable idea.
>
> I was switching on an optional enum today, and naturally gravitated
> towards including nil as a case:
>
> enum Coin {
>   case heads
>   case tails
> }
> var result: Coin?
>
> switch result {
> case heads: print("heads")
> case tails: print("tails")
> case nil: print("not yet flipped") // exhaustive
> }
>
> Doesn't compile, and of course I can if-let or guard to unwrap instead,
> but I like the compactness of this.
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