[swift-users] Non-objc protocol inheritance from objc protocol

[Jordan Rose]

Hi, Pavel. This is definitely supported, and it is indeed a bug that these are not both producing 'true'. We're tracking this as rdar://problem/24453316 <rdar://problem/24453316>.

Jordan


> On Feb 5, 2017, at 03:14, Pavel Ivashkov via swift-users <swift-users at swift.org> wrote:
> 
> Hello,
> 
> What is the current view on inheriting non-objc protocol from objc protocol? Is it supported? Is it a valid construct?
> 
> 
> import Foundation
> 
> @objc protocol Base {}
> 
> protocol Some : Base {}
> 
> class Nada : NSObject, Some {}
> 
> let x: NSObject = Nada()
> 
> print("Nada is Some? \(x is Some)")
> print("Nada is Base? \(x is Base)")
> 
> 
> There are two statements in the docs on @objc attribute:
> a) The compiler also implicitly adds the objc attribute to a class that inherits from another class marked with the objc attribute or a class defined in Objective-C.
> b) Protocols marked with the objc attribute can’t inherit from protocols that aren’t.
> 
> But they don't spec the other way round about protocols.
> 
> 
> Currently the output is
> 
> swift main.swift
> Nada is Some? true
> Nada is Base? false
> 
> Which is not what I would expect.
> 
> Here is extended example: http://stackoverflow.com/q/42023977 <http://stackoverflow.com/q/42023977>
> 
> swift --version
> Apple Swift version 3.0.2 (swiftlang-800.0.63 clang-800.0.42.1)
> Target: x86_64-apple-macosx10.9
> 
> (same on 3.1-dev)
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