[swift-evolution] [pitch] Make swift enum string available to Objc

Michael Ilseman milseman at apple.com
Tue Feb 21 12:31:56 CST 2017

A quick note addressing a misconception that you’ll want to clean up for a formal proposal:

NS_[EXTENSIBLE_]STRING_ENUMs both generate Swift structs, the difference is only in the explicitness of the rawValue initializer. To use the “other direction” analogy, you’d similarly want them to apply for rawValue-ed structs alone. The reasons are the same: only the structs are layout-compatible because enums are integers.

Once you go down this route, perhaps it doesn’t make sense to annotate the struct decls themselves anymore. Maybe you just want more @objc control over bridging the types. For example, maybe you want to introduce a feature so that static members that are layout-compatible with String are bridged as global strings with the supplied name.

> On Feb 20, 2017, at 4:07 PM, Derrick Ho via swift-evolution <swift-evolution at swift.org> wrote:
> Swift should not forsake objective-c.  At least not when it comes enum strings.  Although swift enums are suppose to be swift only, I think we should add a new attribute to slightly relax that.  I think a good attribute would be @objcstring.
> By adding @objcstring, an objective-c exclusive class will be generated.
> @objcstring
> enum Planet {
>   case Jupiter
> }
> I have written up a proposal with more details on what it would look for objective-c.
> https://github.com/wh1pch81n/swift-evolution/blob/swift-enum-objc/proposals/NNNN-Swift-enum-strings-ported-to-Objective-c.md <https://github.com/wh1pch81n/swift-evolution/blob/swift-enum-objc/proposals/NNNN-Swift-enum-strings-ported-to-Objective-c.md>
> If no one objects to this proposal I'll submit it.
> **notes: I am reviving this discussion so that I may submit this for Swift 4 stage 2
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