> On Jan 4, 2016, at 8:49 PM, Félix Cloutier <[email protected]> wrote:
>
> For the folks who don't mix Swift and Objective-C that much, extensions on
> @objc classes are exposed to the Objective-C runtime, so there is a
> discrepancy here. I'm not passionate about the outcome, just dropping the
> info.
Right. I think this is the reason that developers expect members of @objc
protocol extensions to show up in Objective-C, because it automatically happens
for extensions of @objc classes. (We’ve received a number of bug reports about
this)
- Doug
>
> Félix
>
>> Le 4 janv. 2016 à 23:32:25, Douglas Gregor via swift-evolution
>> <[email protected] <mailto:[email protected]>> a écrit :
>>
>> 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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>
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