> On Jan 4, 2016, at 8:54 PM, Kevin Lundberg <ke...@klundberg.com> wrote:
>
> I like this idea, but I would imagine that for an extension with many
> functions in it, requiring @nonobjc on each one would get tedious very fast.
> Could it be required (or at least allowed in addition to per-method
> annotations) at the extension level?:
>
> @objc protocol P {}
>
> @nonobjc extension P {
> func foo() { }
> func bar() { }
> func baz() { }
> func blah() { }
> // etc...
> }
>
> I don’t know if this would have specific implementation ramifications over
> only doing this on each method, if extensions cannot already be modified with
> attributes. I can’t think of a case where I’ve seen annotations added to
> protocol extensions, or any other extensions for that matter.
We have some declaration modifiers (e.g., access-control modifiers) and
attributes (e.g., availability) that distribute in this manner from the
extension to its members. My only hesitation here is that @objc itself doesn’t
distribute in this way, and I’d rather they not be inconsistent.
- Doug
>
>> On Jan 4, 2016, at 11:32 PM, Douglas Gregor via swift-evolution
>> <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote:
>>
>> Hi all,
>>
>> We currently have a bit of a surprise when one extends an @objc protocol:
>>
>> @objc protocol P { }
>>
>> extension P {
>> func bar() { }
>> }
>>
>> class C : NSObject { }
>>
>> let c = C()
>> print(c.respondsToSelector("bar")) // prints "false"
>>
>> because the members of the extension are not exposed to the Objective-C
>> runtime.
>>
>> There is no direct way to implement Objective-C entry points for protocol
>> extensions. One would effectively have to install a category on every
>> Objective-C root class [*] with the default implementation or somehow
>> intercept all of the operations that might involve that selector.
>>
>> Alternately, and more simply, we could require @nonobjc on members of @objc
>> protocol extensions, as an explicit indicator that the member is not exposed
>> to Objective-C. It’ll eliminate surprise and, should we ever find both the
>> mechanism and motivation to make default implementations of @objc protocol
>> extension members work, we could easily remove the restriction at that time.
>>
>> - Doug
>>
>> [*] Assuming you can enumerate them, although NSObject and the hidden
>> SwiftObject cover the 99%. Even so, that it’s correct either, because the
>> root class itself might default such a method, and the category version
>> would conflict with it, so...
>>
>> _______________________________________________
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>> swift-evolution@swift.org <mailto:swift-evolution@swift.org>
>> https://lists.swift.org/mailman/listinfo/swift-evolution
>
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