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

[Geordie Jay]

I am dealing with a variant of this on Android right now. I have just
subclassed e.g. UITapGestureRecognizer to perform the 2nd variant above and
externally accept a closure as its argument. I'm writing this on my phone
so forgive any syntax errors or accidental omissions:

class TapGestureRecognizer: UITapGestureRecognizer {
var onTap: (() -> Void)?
init(onTap: (() -> Void)?) {
self.onTap = onTap
super.init(target: self, action: #selector(internalTapHandler))
}

@objc private func internalTapHandler() {
onTap?()
}
}

class Baz: Foo {
init() {
let tapRecognizer = TapGestureRecognizer(onTap: self.bar)
}
}


Cheers,
Geordie
On Sat 3. Jun 2017 at 16:53, Nate Birkholz via swift-users <
swift-users at swift.org> wrote:

> Thanks, the second had occurred to me, but felt a little too much like in
> practice it would make the code harder to understand.
>
> On Fri, Jun 2, 2017 at 9:58 PM, Zhao Xin <owenzx at gmail.com> wrote:
>
>> 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
>>>
>>>
>>
>
>
> --
> Nate Birkholz
> _______________________________________________
> swift-users mailing list
> swift-users at swift.org
> https://lists.swift.org/mailman/listinfo/swift-users
>
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