> On 10 Oct 2016, at 21:18, Haravikk via swift-evolution
> <swift-evolution@swift.org> wrote:
>
>
>> On 10 Oct 2016, at 14:36, Mateusz Malczak <mate...@malczak.info
>> <mailto:mate...@malczak.info>> wrote:
>>
>>> Can't this problem most easily be solved by a raw value? Like so:
>>>
>>> enum Format : Int {
>>> case small = 30
>>> case medium = 60
>>> case large = 120
>>>
>>> var width:Int { return self.rawValue }
>>> var height:Int { return self.rawValue }
>>> }
>>
>> This only solves a problem when width/height are the same. Im talking
>> here about more general use case when you can assign different values
>> of different types to an enum case. Please refer to the example code:
>> https://swiftlang.ng.bluemix.net/#/repl/57fb98074f9bcf25fdd415d8
>> <https://swiftlang.ng.bluemix.net/#/repl/57fb98074f9bcf25fdd415d8>
>>
>> --
>> | Mateusz Malczak
>
> I know, but what I'm saying is that this problem could be solved in the
> multiple values case by allowing tuples as raw values for enums, since that
> would allow you to specify both width and height. So it'd look something like
> this:
>
> enum Format : (width:Int, height:Int) {
> case small = (30, 30)
> case medium = (60, 60)
> case large = (120, 120)
>
> var width:Int { return self.rawValue.width }
> var height:Int { return self.rawValue.height }
> }
>
> This currently isn't supported as tuples aren't treated as a literal type,
> even when composed of literal types.
>
Nice, that ties in well with a recent post here about deriving enums from other
types:
struct Size {
let width: Double
let height: Double
}
enum Format: Size {
case small = Size(width: 30, height: 30)
case medium = Size(width: 60, height: 60)
}
let format = Format.small
let size = format.width
I’d like that a lot!
> Since enum values can be anything that is representable as literal (except
> arrays, apparently, which I tried but don't seem to work), you can implement
> this with a lot of boiler-plate like so:
>
> struct Dimensions : RawRepresentable, ExpressibleByStringLiteral, Equatable {
> let width:Int, height:Int
> init(width:Int, height:Int) { self.width = width; self.height = height }
>
> init(extendedGraphemeClusterLiteral:String) { self.init(rawValue:
> extendedGraphemeClusterLiteral)! }
> init(stringLiteral:String) { self.init(rawValue: stringLiteral)! }
> init(unicodeScalarLiteral:String) { self.init(rawValue:
> unicodeScalarLiteral)! }
>
> var rawValue:String { return "\(self.width),\(self.height)" }
> init?(rawValue:String) { let parts = rawValue.components(separatedBy:
> ","); self.width = Int(parts[0])!; self.height = Int(parts[1])! }
> }
> func == (lhs:Dimensions, rhs:Dimensions) -> Bool { return (lhs.width ==
> rhs.width) && (lhs.height == rhs.height) }
>
> enum Format : Dimensions {
> case small = "30,30"
> case medium = "60,60"
> case large = "120,120"
>
> var width:Int { return self.rawValue.width }
> var height:Int { return self.rawValue.height }
> }
>
> Not at all pretty, but it works (and I believe the string parsing should
> optimise away in practice).
>
> Anyway, my point is that the best solution to the problem you're trying to
> solve would be to expand the enum raw value support to include tuples.
> _______________________________________________
> swift-evolution mailing list
> swift-evolution@swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution
_______________________________________________
swift-evolution mailing list
swift-evolution@swift.org
https://lists.swift.org/mailman/listinfo/swift-evolution
