Xcode 9.0 Beta：调用 Type.init() 时 swift "cannot init a class object"

Question

我刚刚升级到 Xcode 9.0 Beta，现在我的应用程序在启动时崩溃了。

2017-06-09 14:35:18.817213-0700 recharge-consumer-ios[13524:1720597] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** +[recharge_consumer_ios.SignedOutContainerViewController<0x105c691b8> init]: cannot init a class object.'
*** First throw call stack:
(
0   CoreFoundation                      0x000000010caf4f6b __exceptionPreprocess + 171
1   libobjc.A.dylib                     0x000000010ba3e121 objc_exception_throw + 48
2   CoreFoundation                      0x000000010cb7f6ff +[NSObject(NSObject) init] + 127
3   recharge-consumer-ios               0x0000000105322223 _T021recharge_consumer_ios22RechargeViewControllerCACycfCTD + 19

失败的调用是（简化）：

func setAndRefreshChildViewControllersWithTypes(_ types: [MyViewControllerProtocol.Type]) {
    for type in types {
        let controller = type.init() as! UIViewController // This is what crashes
    }
    ...
}

其中 MyViewControllerProtocol 是：

protocol MyViewControllerProtocol {
    // some other fields here too
    init()
}

失败的实例如下所示：

class SignedOutContainerViewController: MyViewController {

    required init() {
        super.init(nibName: "SignedOutContainerViewController")
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

其中 MyViewController 是：

class MyViewController: UIViewController, MyViewControllerProtocol {
    required init() {
        fatalError("init has not been implemented")
    }

    init(nibName nibNameOrNil: String?) {
        super.init(nibName: nibNameOrNil, bundle: nil)
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

知道出了什么问题，或者有其他地方可以查看的指示吗？ Xcode 9.0 测试版 (9M136h)，swift 3.

Answer 1

对崩溃的方法使用@objc

Answer 2

我想跟进，因为已接受的答案对我不起作用。所有这些都是在操场上使用 swift 4.0 开发快照工具链进行测试的 Xcode 从 2017 年 6 月 12 日开始。

这将因运行时异常而失败

import Foundation

public protocol MyProtocol {
    init()
}

@objc // This doesn't work
public class MyClass: NSObject, MyProtocol {

    @objc // This doesn't work either
    required public override init() {
        super.init()
    }
}

let anonymousType: AnyClass = MyClass.self

let metaType: MyProtocol.Type = anonymousType as! MyProtocol.Type
let instance = metaType.init()

对我来说，这并不像用 @objc 标记 class 或方法那么简单。我找到了 2 个适合我的解决方案。

标记class决赛

import Foundation

public protocol MyProtocol {
    init()
}

final public class MyClass: NSObject, MyProtocol {

    required public override init() {
        super.init()
    }
}

let anonymousType: AnyClass = MyClass.self

let metaType: MyProtocol.Type = anonymousType as! MyProtocol.Type
let instance = metaType.init()

标记协议@objc

import Foundation

@objc
public protocol MyProtocol {
    init()
}

public class MyClass: NSObject, MyProtocol {

    required public override init() {
        super.init()
    }
}

let anonymousType: AnyClass = MyClass.self

let metaType: MyProtocol.Type = anonymousType as! MyProtocol.Type
let instance = metaType.init()

Xcode 9.0 Beta：调用 Type.init() 时 swift "cannot init a class object"

Xcode 9.0 Beta: swift "cannot init a class object" when calling Type.init()

xcode

ios

swift

swift3

xcode9-beta