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

[Nate Birkholz]

I briefly considered something like this but didn't explore it. Elegant.

Sent from my iPhone, please excuse brevity and errors

> On Jun 3, 2017, at 9:38 PM, Geordie Jay <geojay at gmail.com> wrote:
> 
> 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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-users/attachments/20170604/17544f1e/attachment.html>