[swift-evolution] [Proposal] Allow enumerating cases in enumerations

[Charlie Monroe]

This is mentioned in Gabriel's proposal:

> Implement a native .cases static var for all enumerations without associated values


But as has been mentioned in the discussion, this was mentioned by Brent:

> In previous discussions, the core team specifically asked that this be opt-in so that types which don't want it don't need to "pay" for it.



> On Jul 5, 2016, at 12:43 PM, James Campbell <james at supmenow.com> wrote:
> 
> Maybe a way we could opt in is by only doing this for enums with out turples?
> 
> i.e
> 
> enum ABTestingBrah {
> 
> case A
> case B
> 
> }
> 
> I'm not sure if enums that take turples would need this functionality.
> 
> ___________________________________
> 
> James⎥Head of Trolls
> 
> james at supmenow.com <mailto:james at supmenow.com>⎥supmenow.com <http://supmenow.com/>
> Sup
> 
> Runway East
> 
> 
> 10 Finsbury Square
> 
> London
> 
> 
> EC2A 1AF 
> 
> 
> On 5 July 2016 at 11:39, Charlie Monroe <charlie at charliemonroe.net <mailto:charlie at charliemonroe.net>> wrote:
> Example:
> 
> enum MediaKind {
> 	case HomeVideo, Movie, MusicVideo, TVShow
> 
> 	var localizedName: String { ... }
> }
> 
> let popUpButton: NSPopUpButton = ...
> for kind in MediaKind.allKinds {
> 	popUpButton.addItemWithTitle(kind.localizedName)
> }
> 
> And many, many more.
> 
> 
>> On Jul 5, 2016, at 12:33 PM, James Campbell via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>> Would love a real life scenario of why you would need this.
>> 
>> ___________________________________
>> 
>> James⎥Head of Trolls
>> 
>> james at supmenow.com <mailto:james at supmenow.com>⎥supmenow.com <http://supmenow.com/>
>> Sup
>> 
>> Runway East
>> 
>> 
>> 10 Finsbury Square
>> 
>> London
>> 
>> 
>> EC2A 1AF 
>> 
>> 
>> On 4 July 2016 at 02:36, Gabriel Lanata via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> Hello, this has been proposed multiple times before in different ways. 
>> 
>> Link to detailed proposal draft:
>> https://github.com/gabriellanata/swift-evolution/blob/master/proposals/NNNN-allow-enumerating-cases-in-enumerations.md <https://github.com/gabriellanata/swift-evolution/blob/master/proposals/NNNN-allow-enumerating-cases-in-enumerations.md>
>> 
>> It is currently not possible to enumerate through all the possible cases of an enumeration object without adding a hardcoded value or recurring to unsafe workarounds. The proposal is to add a method of obtaining an array or set of all the possible cases natively for enumerations without associated values.
>> 
>> The proposed solution is to implement a native `.cases` static var for all enumerations without associated values. This would provide a strict type-safe way of enumerating though the possible cases without risking runtime errors. The resulting code is a lot cleaner and less prone to errors caused by forgetting to update the hardcoded values when modifying cases.
>> 
>> Resulting code:
>>  
>>    enum PokemonType {
>>        case Fire, Grass, Water, Wind
>>    }
>>    for pokemonType in PokemonType.cases {
>>        // Do stuff
>>    }
>>    PokemonType.cases.count // Returns 4
>> 
>> 
>> -------
>> Gabriel
>> 
>> 
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>> 
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> 

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