[swift-users] Attempting to call default protocol implementation crashes Playground

[Игорь Никитин]

Right, it’s a recursion, because this 

(self as FooPro).fooFunc()

Will call FooClass’s  method implementation

You can read more about dispatch rules here: https://medium.com/ios-os-x-development/swift-protocol-extension-method-dispatch-6a6bf270ba94#.hkh1rc56p <https://medium.com/ios-os-x-development/swift-protocol-extension-method-dispatch-6a6bf270ba94#.hkh1rc56p>



> 16 нояб. 2016 г., в 4:29, Rick Mann via swift-users <swift-users at swift.org> написал(а):
> 
> Okay. I coudln't find official documentation on this, and I don't currently need to do this, but wanted to fully understand it.
> 
>> On Nov 15, 2016, at 17:27 , zh ao <owenzx at gmail.com> wrote:
>> 
>> 'Default' implementation in protocol extension is used as fail safe. You should not consider it like something super class does. If you want it that way, use class inheritance instead.
>> 
>> Zhaoxin
>> 
>> Get Outlook for iOS
>> 
>> _____________________________
>> From: Rick Mann via swift-users <swift-users at swift.org>
>> Sent: 星期三, 十一月 16, 2016 07:51
>> Subject: Re: [swift-users] Attempting to call default protocol implementation crashes Playground
>> To: Dan Loewenherz <dan at lionheartsw.com>
>> Cc: swift-users <swift-users at swift.org>
>> 
>> 
>> Well, this is a standard protocol default implementation. I was experimenting to see if it was possible to call the default implementation after providing a concrete implementation.
>> 
>>> On Nov 15, 2016, at 14:47 , Dan Loewenherz <dan at lionheartsw.com> wrote:
>>> 
>>> What are you trying to accomplish here, more concretely?
>>> 
>>> My first thought is that you shouldn't implement the same function in both a protocol extension and a conforming class. Why not just give them different names and call the function from within the extension instead of from the class? E.g.
>>> 
>>> protocol FooPro {
>>> func _fooFunc()
>>> }
>>> 
>>> extension FooPro {
>>> func fooFunc() {
>>> print("fooFunc default")
>>> _fooFunc()
>>> }
>>> }
>>> 
>>> class FooClass: FooPro {
>>> func _fooFunc() {
>>> print("fooFunc FooClass")
>>> }
>>> }
>>> 
>>> let fc = FooClass()
>>> fc.fooFunc()
>>> 
>>> Dan
>>> 
>>> On Tue, Nov 15, 2016 at 4:28 PM, Rick Mann via swift-users <swift-users at swift.org> wrote:
>>> The following gives Xcode 8.1 a very hard time. Eventually I get a Bad Access on the last line. I'm guessing it's a recursive call. Is there any way to call the default implementation from a "real" implementation?
>>> 
>>> protocol FooPro
>>> {
>>> func fooFunc()
>>> }
>>> 
>>> extension FooPro
>>> {
>>> func
>>> fooFunc()
>>> {
>>> print("fooFunc default")
>>> }
>>> }
>>> 
>>> class FooClass : FooPro
>>> {
>>> func
>>> fooFunc()
>>> {
>>> (self as FooPro).fooFunc()
>>> print("fooFunc FooClass")
>>> }
>>> }
>>> 
>>> let fc: FooPro = FooClass()
>>> fc.fooFunc()
>>> 
>>> 
>>> Thanks!
>>> 
>>> 
>>> --
>>> Rick Mann
>>> rmann at latencyzero.com
>>> 
>>> 
>>> _______________________________________________
>>> swift-users mailing list
>>> swift-users at swift.org
>>> https://lists.swift.org/mailman/listinfo/swift-users
>>> 
>> 
>> 
>> -- 
>> Rick Mann
>> rmann at latencyzero.com
>> 
>> 
>> _______________________________________________
>> swift-users mailing list
>> swift-users at swift.org
>> https://lists.swift.org/mailman/listinfo/swift-users
>> 
>> 
> 
> 
> -- 
> Rick Mann
> rmann at latencyzero.com <mailto:rmann at latencyzero.com>
> 
> 
> _______________________________________________
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> swift-users at swift.org <mailto:swift-users at swift.org>
> https://lists.swift.org/mailman/listinfo/swift-users <https://lists.swift.org/mailman/listinfo/swift-users>
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