[swift-evolution] Variable with generic protocol type
Ross O'Brien
narrativium+swift at gmail.com
Fri Jun 16 11:33:24 CDT 2017
As I understand it, and someone please correct me if I'm wrong, you've just
described *existentials*, which Swift doesn't fully support yet but which
are on the Generics Manifesto.
It would be nice to declare or cast a variable as 'conforms to protocol X
with associated type known to be Y' or 'conforms to protocol X with
associated type known to conform to Z'.
I don't know what syntax has been suggested / agreed upon for either of
these, though.
On Fri, Jun 16, 2017 at 3:13 PM, Rtnm Nosurname via swift-evolution <
swift-evolution at swift.org> wrote:
> Hello.
>
> Sorry, but C# code:
>
> interface IValidator<T> {
> bool validate(T value);
> }
> IValidator<String> validator;
>
> Easy, simple and clear.
>
> Swift:
>
> protocol PValidator {
> associatedtype ValidateType
> func validate(value: ValidateType) -> Bool
> }
> var validator: ????
>
> it can be so:
> var validator: PValidator where ValidateType == String
>
> or
> var validator: <T: PValidator> where ValidateType == String
>
> or
> var validator: PValidator<ValidateType == String>
>
> or
> typealias StringValidator = PValidator<ValidateType == String>
> var validator: StringValidator
>
> No matter how, but it should be.
>
> What alternatives offers swift?
> _______________________________________________
> swift-evolution mailing list
> swift-evolution at swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution
>
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