swift - 继承自@objc协议(protocol)

Question

我有这个协议(protocol)继承

@objc protocol Base {}

protocol Some : Base {}

检查它的代码main.swift:

import Foundation

class Model1 : NSObject {}

extension Model1 : Some {}


class Model2 : NSObject, Some {}


func test() {
    let m1: NSObject = Model1()
    let m2: NSObject = Model2()

    print("m1 is Some? \(m1 is Some)")
    print("m2 is Some? \(m2 is Some)")

    print("m1 is Base? \(m1 is Base)")
    print("m2 is Base? \(m2 is Base)")
}

test()

有趣的是，swiftc 和 swift 的输出不同

swiftc main.swift && ./main
m1 is Some? true
m2 is Some? true
m1 is Base? false
m2 is Base? false

对比

swift main.swift
m1 is Some? true
m2 is Some? true
m1 is Base? true
m2 is Base? false

但问题是 – 为什么我不能将它们中的任何一个转换为 Base？

如果我将 @objc 添加到 Some，那么每个测试都会通过 true。但我现在不能这样做，这是另一个 SO ( see here ) 的主题。

swiftc --version
Apple Swift version 3.0.2 (swiftlang-800.0.63 clang-800.0.42.1)
Target: x86_64-apple-macosx10.9

Answer 1

来自 swift-users ，似乎是一个已知问题，需要修复:https://bugs.swift.org/browse/SR-1175

现在也报告为 https://bugs.swift.org/browse/SR-3882