[swift-evolution] Proposal: label-only constructors

[Harlan Haskins]

Also I think it’d be cleaner to just accept an enum in one initializer

enum KeyType {
    case RSA
    case Curve25519
    case AES
}

Then you get that semantic niceness of:

init(keyType: .RSA)
init(keyType: .Curve25519)
init(keyType: .AES)

— Harlan

> On Dec 13, 2015, at 11:41 AM, Sean Heber via swift-evolution <swift-evolution at swift.org> wrote:
> 
> In this particular example, perhaps Key should be an enum instead of a struct.
> 
> l8r
> Sean
> 
> Sent from my iPad
> 
> On Dec 13, 2015, at 10:07 AM, ilya via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
> 
>> Good point on that. I still think the best solution is to take the existing syntax of
>> 
>> 
>> struct Key {
>>     init(forRSA:Void) { /* */ }
>>     init(forCurve25519:Void) { /* */ }
>>     init(forAES:Void) { /* */ }
>> }
>> 
>> let a = Key(forRSA: ())
>> 
>> or 
>> 
>> let empty: Void = ()
>> let c = Key(forAES: empty)
>> 
>> and make it somewhat easier to read.  Perhaps
>> 
>> let b = Key(forCurve25519: _ )
>> 
>> I think many people will read Key(forAES) as Key.init(_: forAES), so that may be not the best expression here.
>> 
>> 
>> 
>> On Sun, Dec 13, 2015 at 4:21 PM, Drew Crawford <drew at sealedabstract.com <mailto:drew at sealedabstract.com>> wrote:
>> 
>>> On Dec 13, 2015, at 7:13 AM, ilya <ilya.nikokoshev at gmail.com <mailto:ilya.nikokoshev at gmail.com>> wrote:
>>> 
>>> You can easily call a private parametrized init from a class function though. 
>> 
>> 
>> Sure, but we're just shuffling the deck.  We've gone from a bad public API to a bad private API.
>> 
>> Actually, it's worse, because we now have BOTH a bad private API AND a bad public API.  There is a reason that NSData.dataWithData(...) is a Swift compile error.
>> 
>> The (ab)use of class functions as constructors is a holdover from ObjC times.  If you want to make an instance in Swift, you should type ClassName( and see what autocomplete suggests; you should not have to read through the documentation of class functions to see if they are secretly constructors that have been filed at the wrong shelf in the library.
>> 
>> 
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