[swift-evolution] [Pitch] Allow nested protocol declarations

[Howard Lovatt]

+1 very handy to associate types together

On Friday, 29 April 2016, Michael Peternell via swift-evolution <
swift-evolution at swift.org> wrote:

> I think that would be a good feature.
>
> > Am 28.04.2016 um 19:15 schrieb Brad Hilton via swift-evolution <
> swift-evolution at swift.org <javascript:;>>:
> >
> > Type nesting allows some convenient and straightforward semantics that
> we see inside the Swift standard library such as views on String like
> String.CharacterView, String.UnicodeScalarView, etc. However a protocol
> cannot be nested in a type and gives a non-obvious error that the
> “Declaration is only valid at file scope.” Just as other nested types allow
> proper contextual scoping, a nested protocol could make a lot sense for a
> number of patterns. For example, there are many “Delegate” protocols
> throughout the Cocoa frameworks. Here’s a controller/delegate pattern
> before and after type nesting:
> >
> > // Without type nesting
> >
> > protocol MyControllerDelegate : class {
> >
> > }
> >
> > class MyController {
> >
> >     weak var delegate: MyControllerDelegate?
> >
> > }
> >
> > // With type nesting
> >
> > class MyController {
> >
> >     weak var delegate: Delegate?
> >
> >     protocol Delegate : class {
> >
> >     }
> >
> > }
> >
> > Though the change is mostly semantics, it does allow an explicit
> association between My Controller and the Delegate instead of only a named
> association. It also cleans up the module name space like other nested
> types and makes associated protocols more discoverable in my opinion.
> >
> > I’d love to hear everyone’s thoughts.
> >
> > Brad Hilton
> > _______________________________________________
> > swift-evolution mailing list
> > swift-evolution at swift.org <javascript:;>
> > https://lists.swift.org/mailman/listinfo/swift-evolution
>
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-- 
-- Howard.
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