Codable如何适应iOS恢复过程？

Question

在AppDelegate.swift中，我有：

func application(_ application: UIApplication, shouldRestoreApplicationState coder: NSCoder) -> Bool {
    return true
}

在状态恢复期间，iOS将调用我的encodeRestorableState() & decodeRestorableState()类方法。

关于状态恢复，Codable是如何工作的？iOS调用什么以及如何绑定我的可编码结构和类？

Answer 1

encodeRestorableState(with:)向您传递一个NSCoder实例。恢复状态所需的任何变量都必须在这里使用encode(_:forKey:)和此编码器进行编码，因此必须符合Codable。

decodeRestorableState(with:)将这个相同的编码器传递到函数体中。您可以使用编码时使用的密钥访问解码器中的属性，然后将它们设置为实例变量，或者使用它们来配置控制器。

例如：

import UIKit

struct RestorationModel: Codable {
   static let codingKey = "restorationModel"
   var someStringINeed: String?
   var someFlagINeed: Bool?
   var someCustomThingINeed: CustomThing?
}

struct CustomThing: Codable {
   let someOtherStringINeed = "another string"
}

class ViewController: UIViewController {
   var someStringIDoNotNeed: String?
   var someStringINeed: String?
   var someFlagINeed: Bool?
   var someCustomThingINeed: CustomThing?

   override func encodeRestorableState(with coder: NSCoder) {
      super.encodeRestorableState(with: coder)
      let restorationModel = RestorationModel(someStringINeed: someStringINeed,
                                              someFlagINeed: someFlagINeed,
                                              someCustomThingINeed: someCustomThingINeed)

      coder.encode(restorationModel, forKey: RestorationModel.codingKey)
   }

   override func decodeRestorableState(with coder: NSCoder) {
      super.decodeRestorableState(with: coder)
      guard let restorationModel = coder.decodeObject(forKey: RestorationModel.codingKey) as? RestorationModel else {
         return
      }
      someStringINeed = restorationModel.someStringINeed
      someFlagINeed = restorationModel.someFlagINeed
      someCustomThingINeed = restorationModel.someCustomThingINeed
   }
}