Xcode 9.0 Beta：调用 Type.init() 时快速"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。

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
}
...
}

MyViewControllerProtocol在哪里：

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，或者指示在哪里看吗？ Xcode 9.0 Beta (9M136h)， swift 3.

Answer 1

我想跟进，因为接受的答案对我不起作用。所有这些都在操场上进行了测试，使用 6/12/17 开始的 Xcode 的 swift 4.0 开发快照工具链。

这将失败并出现运行时异常

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标记类或方法那么简单。我找到了 2 个适合我的解决方案。

1. 标记课程最终

   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()
   

2. 将协议标记为@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()
   

Answer 2

对崩溃的方法使用 @objc