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).
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.
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.
- 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
P.S. This is rdar://problem/22296436 for anyone else at Apple.
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