Hi, Marco. The limitation here is that you can’t use swift_name (or
NS_SWIFT_NAME) to add members to someone else’s type (more precisely, a type
not declared in your module’s headers). You’re not the first to be dissatisfied
with this restriction, though, particularly since as you point out you can just
add a Swift-side extension to do the same thing. Within Apple,
rdar://problem/31877728 <rdar://problem/31877728> tracks making the feature
more general.
Similarly, the automatic import-as-member feature for
NS_EXTENSIBLE_STRING_ENUMs is also only enabled for constants in the same
module as the type. I’m not sure we want to rock the boat on that one.
Jordan
> On Sep 27, 2017, at 07:07, Marco Masser via swift-users
> <swift-users@swift.org> wrote:
>
> Hi,
>
> Swift 4 and the macOS 10.13 SDK added a new NSAttributedStringKey type for
> the keys that NSAttributedStrings use. The keys are then defined in an
> extension of NSAttributedStringKey, essentially like this in AppKit:
>
> // AppKit/NSAttributedString.h (Objective-C)
> extern NSAttributedStringKey NSFontAttributeName;
>
> // Generated Swift Interface
> extension NSAttributedStringKey {
> public static let font: NSAttributedStringKey
> }
>
>
> How do I get my own custom NSAttributedStringKeys to be imported this way?
> When I do it like AppKit, it doesn’t seem to work:
>
> // My Objective-C header
> extern NSAttributedStringKey ODRolloverTokenAttributeName;
>
> // Generated Swift Interface
> static let ODRolloverTokenAttributeName: NSAttributedStringKey
>
>
> That is obviously not the same. I tried using the NS_SWIFT_NAME macro, but
> that results in the symbol disappearing in Swift completely:
>
> // My Objective-C header
> extern NSAttributedStringKey ODRolloverTokenAttributeName
> NS_SWIFT_NAME(NSAttributedStringKey.rolloverToken);
>
>
> I also tried to use the swift_name attribute that is used by the
> NS_SWIFT_NAME macro and that is even mentioned in SE-0044 for exactly this
> purpose, but the symbol still disappears:
> https://github.com/apple/swift-evolution/blob/master/proposals/0044-import-as-member.md#swift_name-attribute
>
> <https://github.com/apple/swift-evolution/blob/master/proposals/0044-import-as-member.md#swift_name-attribute>
>
> extern const NSAttributedStringKey ODRolloverTokenAttributeName
> __attribute__((swift_name("NSAttributedStringKey.rolloverToken")));
>
>
> What works is to manually define it in an extension like this, but that’s no
> fun:
>
> // My Objective-C header
> extern NSAttributedStringKey ODRolloverTokenAttributeName
> NS_REFINED_FOR_SWIFT;
>
> extension NSAttributedStringKey {
> static let rolloverToken =
> NSAttributedStringKey(__ODRolloverTokenAttributeName.rawValue)
> }
>
>
> Is there no way to import this automatically? Was this functionality removed
> before release even though it was mentioned in SE-0044?
>
> Cheers,
>
> Marco
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