[swift-users] Calling default implementation of protocol methods as selectors

[Zhao Xin]

I found two workarounds.

1.

protocol Foo: class {

    func bar()

}


class Base:Foo {

    @objc func bar() {

        print("bar")

    }

}


class Baz: Base {

    override init() {

        super.init()

        let tapRecognizer = UITapGestureRecognizer(target: self, action:
#selector(bar))

    }

}

2.

protocol Foo: class {

    func bar()

}


extension Foo {

    func bar() {

        print("bar")

    }

}


class Baz: Foo {

    init() {

        let tapRecognizer = UITapGestureRecognizer(target: self, action:
#selector(delegate))

    }



    @objc func delegate() {

        bar()

    }

}


Zhao Xin






On Sat, Jun 3, 2017 at 10:35 AM, Nate Birkholz via swift-users <
swift-users at swift.org> wrote:

> protocol Foo: class {
>     func bar()
> }
>
> extension Foo {
>     func bar() {
>          print("bar")
>     }
> }
>
> class Baz: Foo {
>     init() {
>         let tapRecognizer = UITapGestureRecognizer(target: self, action:
> #selector(bar))
>     }
> }
>
> the #selector tells me: "Argument of '#selector' refers to instance method
> 'bar()' that is not exposed to Objective-C" and asks me to add @objc to the
> method definition.
>
> Adding @objc to the method tells me: "@objc can only be used with members
> of classes, @objc protocols, and concrete extensions of classes"
>
> Adding @objc to the protocol doesn't fix it, just introduces new issues.
>
> "dynamic" cannot be applied to a protocol, so cannot be used
> alternatively.
>
> Is there a way to get around this? If a method is called by a gesture
> recognizer, is there no way to have a default protocol implementation? I'd
> like to use default implementations if possible to make my code more DRY.
>
> Is there a roadmap/plan for swift-native selector dispatch?
>
> Thanks. I look forward to the inevitable reply revealing the dumb thing I
> missed. :)
>
> --
> Nate Birkholz
>
> _______________________________________________
> swift-users mailing list
> swift-users at swift.org
> https://lists.swift.org/mailman/listinfo/swift-users
>
>
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