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.
Félix > Le 4 janv. 2016 à 23:32:25, Douglas Gregor via swift-evolution > <swift-evolution@swift.org> 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... > > _______________________________________________ > swift-evolution mailing list > swift-evolution@swift.org > https://lists.swift.org/mailman/listinfo/swift-evolution
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