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

[Zhao Xin]

I was not talking about the formatting. I am talking about the
implementation.

You can't use `self` before you call `super.init` as you did now. If
 changing your implementation to called `super.init` and then call `self`
in `super.init` again. You would have called `super.init` twice. I don't
know what that means. But it smells bad.

Zhaoxin

On Sun, Jun 4, 2017 at 12:51 PM, Geordie Jay <geojay at gmail.com> wrote:

> Thanks for the amendment, and sorry for the (lack of) formatting. I
> painstakingly typed that on my phone with manually-spaced indenting, which
> the Inbox app unhelpfully removed entirely when I pressed send. Pasting
> into Xcode should do the trick though..
>
> Geordie
>
> On Sun 4. Jun 2017 at 14:49, Zhao Xin <owenzx at gmail.com> wrote:
>
>> You should change to another way. Using `self` in `super.init` is not
>> allowed.
>>
>> Zhaoxin
>>
>> On Sun, Jun 4, 2017 at 12:38 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
>>>>
>>>
>>
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