swift - 协议(protocol)崩溃代码执行的约束

Question

我得到了这段代码:

import UIKit

protocol Test where Self: UIView {
    func printAnything()
}

class MyView: UIView, Test {
    func printAnything() {
        print("Anything")
    }
}

let myView: Test = MyView()
myView.printAnything()

约束是:where Self: UIView

当您将其粘贴到 playground 中时，它会在运行时崩溃并出现以下错误:

error: Execution was interrupted, reason: EXC_BAD_ACCESS (code=1, address=0x0).

移除约束，确实移除运行时错误并打印“Anything”。为什么添加的约束会在运行时崩溃？

运行 XCode 9.3 Swift 4.1

Answer 1

为了将其限制为 Objective-C 类型，协议(protocol)需要为 @objc:

@objc protocol Test where Self: UIView {
    func printAnything()
}

这是一个已知缺陷:SR-7068 .