> On Jun 27, 2016, at 1:26 PM, Jordan Rose via swift-evolution
> <[email protected]> wrote:
>
> Hey, all. An engineer at Apple noticed the following behavior:
>
> 1. class Foo: NSObject → exposed to Objective-C, Swift-style (mangled)
> runtime name
> 2. @objc class Foo: NSObject → exposed to Objective-C, Swift-style (mangled)
> runtime name
> 3. @objc(Foo) class Foo: NSObject → exposed to Objective-C, unmangled runtime
> name
>
> (and 4. @objc class Foo → illegal, classes must have ObjC heritage to be
> @objc.)
>
> They specifically observed that (1) and (2) have the same behavior, and
> suggested that maybe (2) should be shorthand for (3).
I actually wonder why NSObject subclasses magically appear in the generated
header when they aren’t marked @objc. If anything I’d say we should remove that
behavior.
>
> Pros:
> - There aren't two ways to spell (1).
> - Removing the mangling (and module uniquing) from the runtime name is
> probably one of the most common uses of @objc on a class.
Another really common case (at least in our mixed codebase) is bridging to give
the class a “private” name in Swift but a sensible name in Objective-C because
we have a sensible struct or generic type in Swift, don’t want Swift consumers
to use the @objc type, yet need to provide a bridged interface to Objective-C.
We do the same with methods too.
@objc(Tile)
public class _objc_Tile: NSObject { }
>
> Cons:
> - It's a source-breaking change, for all that the "@objc" in (2) is redundant.
> - For protocols, (1) and (2) are not equivalent, because @objc isn't
> inherited there.
I’d favor consistency even if (1) and (2) are redundant.
> - Mangling is used to namespace class names at run time; if you drop that,
> the ObjC name should probably have a prefix. (This applies more to frameworks
> than apps, though.)
>
> There are probably people who say that last con applies to the generated
> header as well: we shouldn't put (1) or (2) into the generated header because
> the ObjC name might conflict with another class at compile time. This is
> valid, but probably too drastic a change at this point.
>
> So, what does everyone think? I'm leaning towards "no change" because it's a
> bit subtle and not a big enough win, but if there's widespread support for
> this I'll pull it into a proposal.
>
> Jordan
Given other priorities I’d lean toward no change.
Russ
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