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我需要将用户创建的 ViewControllers 存储到一个 json 文件中，我需要稍后在同一设备或不同设备上重新创建它们。

ViewController 在情节提要中可用，但我无法在 init（来自解码器：解码器）函数中正确实例化它们。

这是要保存和恢复的 ViewController。

class SecondViewController: UIViewController, Encodable, Decodable {
@IBOutlet weak var textField: UITextField!

   private var restoreText: String?

   enum CodingKeys: CodingKey {
      case textField
   }

   func encode(to encoder: Encoder) throws {
      var container = encoder.container(keyedBy: CodingKeys.self)
      try container.encode(textField.text, forKey: .textField)
   }

   required init(from decoder: Decoder) throws {
       let container = try decoder.container(keyedBy: CodingKeys.self)
       restoreText = try? container.decode(String.self, forKey: .textField)
       super.init(nibName: "", bundle: nil)
   }

   required init?(coder: NSCoder) {
       super.init(coder: coder)
   }

   override func viewDidLoad() {
       super.viewDidLoad()
       if let text = restoreText {
          textField.text = text
       }
   }

   @IBAction func save(_ sender: Any) {
      do {
        let jsonData = try JSONEncoder().encode(self)
        let s = String(data: jsonData, encoding: .ascii)
        print("Widgets \(s!)")

        let filename = getDocumentsDirectory().appendingPathComponent("output.txt")
        try jsonData.write(to: filename)
      } catch {
        print(error.localizedDescription)
      }
  }
}

这是我从 json 文件加载控制器并尝试重新创建它的地方。

...

do {
      let filename = getDocumentsDirectory().appendingPathComponent("output.txt")
      let jsonData = try Data(contentsOf: filename)
      if let s = String(data: jsonData, encoding: .ascii) {
         let controller = try JSONDecoder().decode(SecondViewController.self, from: jsonData)
         let frame = CGRect(x: 0, y: 0, width: view.frame.width * 0.8, height: view.frame.height * 0.8)
         controller.view.frame = frame
         controller.view.center = view.center
         view.addSubview(controller.view)
         addChild(controller)
      }
    } catch {
        print(error.localizedDescription)
    }
...

运行此代码，我收到以下错误：

*** Assertion failure in -[UINib initWithNibName:directory:bundle:], /AppleInternal/BuildRoot/Library/Caches/com.apple.xbs/Sources/UIKitCore_Sim/UIKit-3920.26.113/UINib.m:97
2020-04-18 09:44:03.543891+0200 ViewControllerSerialization[7764:504964] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Invalid parameter not satisfying: (name != nil) && ([name length] > 0)'

据我了解，此错误是因为尚未从情节提要中加载控制器。

问题是如何在 init(from decoder: Decoder) 函数中从情节提要中正确初始化 ViewController？

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