[swift-evolution] [Idea] Find alternatives to `switch self`

[Taras Zakharko]

This is what happens if you don’t follow the swift-evolution list for a while… I have send a very similar suggestion to the list today (but mine focuses more on methods). Didn’t mean to plagiarise your idea, sorry! Maybe we should bring the two of them together. 

Best, 

 Taras

> On 23 Mar 2016, at 11:13, Brent Royal-Gordon via swift-evolution <swift-evolution at swift.org> wrote:
> 
> If you've written enums before, you've no doubt noticed the irritating phenomenon of `switch self` being absolutely everywhere. I first discovered this in some of my very first Swift code, code so old we were still using the `T[]` shorthand syntax:
> 
>    enum Suit: Int {
>        case Hearts, Spades, Diamonds, Clubs
> 
>        static var all: Suit[] { return [ Hearts, Spades, Diamonds, Clubs ] }
> 
>        var description: String {
>            switch(self) {
>            case .Hearts:
>                return "♥️"
>            case .Spades:
>                return "♠️"
>            case .Diamonds:
>                return "♦️"
>            case .Clubs:
>                return "♣️"
>            }
>        }
> 
>        var isRed: Bool {
>            switch(self) {
>            case .Hearts, .Diamonds:
>                return true
>            case .Spades, .Clubs:
>                return false
>            }
>        }
>    }
> 
> It would be nice if we could somehow eliminate that. I have two suggestions:
> 
> * Implicitly switch on `self` at the top level of a function or accessor (or at least an enum one with top-level `case` statements).
> 
>    enum Suit: Int {
>        case Hearts, Spades, Diamonds, Clubs
> 
>        static var all = [ Hearts, Spades, Diamonds, Clubs ]
> 
>        var description: String {
>        case .Hearts:
>            return "♥️"
>        case .Spades:
>            return "♠️"
>        case .Diamonds:
>            return "♦️"
>        case .Clubs:
>            return "♣️"
>        }
> 
>        var isRed: Bool {
>        case .Hearts, .Diamonds:
>            return true
>        case .Spades, .Clubs:
>            return false
>        }
>    }
> 
> * Allow you to attach member definitions to particular cases. It would be an error if they didn't all define the same members, unless there was a top-level catchall.
> 
>    enum Suit: Int {
>        var isRed: Bool { return false }
> 
>        case Hearts {
>            let description: String { return "♥️" }
>            let isRed: Bool { return true }
>        }
>        case Spades {
>            let description: String { return  "♠️" }
>        }
>        case Diamonds {
>            let description: String { return  "♦️" }
>            let isRed: Bool { return true }
>        }
>        case Clubs {
>            let description: String { return  "♣️" }
>        }
> 
>        static var all = [ Hearts, Spades, Diamonds, Clubs ]
>    }
> 
> Any thoughts? This has, to be honest, bothered me since approximately the third day I used the language; I'd love to address it sooner or later.
> 
> -- 
> Brent Royal-Gordon
> Architechies
> 
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