[SR-492] Protocol extenstion methods aren't exposed to Objective-C

[swift-ci]

Previous ID	SR-492
Radar	None
Original Reporter	aleksanderkania (JIRA User)
Type	Bug
Status	Reopened
Resolution

Additional Detail from JIRA

Votes	5
Component/s	Compiler
Labels	Bug
Assignee	None
Priority	Medium

md5: 5ed2a55af47268aca30c35583bd87d96

is duplicated by:

• SR-942 Cannot provide default implementation of @objc protocol via extension
• SR-1230 Using a Selector("function") does not work when the "function" is defined via a Protocol Extension
• SR-9676 Default implementation for optional protocol functions not invoked

Issue Description:

When class conform the protocol that supplies some method and if the method have default implementation in protocol extension then _respondsToSelector _method return false.

protocol SomeProtocol{
    func foo()->Void
}

extension SomeProtocol{
    func foo()->Void{
        // do something
    }
}

class SomeClass : NSObject, SomeProtocol{
}

let some = SomeClass()
some.respondsToSelector("foo")

[phausler]

respondsToSelector is just a thin veil on class_respondsToSelector so this would be more the objc runtime's domain than Foundation. However is it the case that the protocol would have to have some decorator to be exposed as objc for this to work?

[belkadan]

Right, methods in protocol extensions are not exposed to Objective-C, ever. It's a little unfortunate that we don't have a way to manually do that from the class, though; if you redeclare the method you can't use the default implementation.

[belkadan]

SR-3349 has a bit more discussion on why this isn't really implementable.

[belkadan]

…sorry, I missed my own comment about having it happen manually in the class somehow.

[swift-ci]

Comment by Ilya Kulakov (JIRA)

I faced the similar problem: I have an existing Objective-C protocol with a method which I would like to refine for Swift to use Tuples instead of unsafe pointers. However it does seem to be possible.