ios - UserDefaults 编码失败

Question

将复杂数据存储到 UserDefaults 时，出现异常。代码如下。

写入变量c时发生异常。

struct MyData : Codable {
  var v1 : Int
  var v2 : Int
  var v3 : Int
}


final class AllData : NSObject {

  var a : Int =  0

  var b  = [String : Int]()
  var c  = [String : MyData]()



  func loadSettings()
  {
    let userDefaults = UserDefaults.standard

    if let v = userDefaults.object(forKey: “A”) as? Int {
      self.a = v
    }


    if let v = userDefaults.object(forKey: “B”) as? [String : Int] {
      self.b = v
    }


    guard let decodedNSData = userDefaults.object(forKey: “C”) as? NSData,
      let v = (NSKeyedUnarchiver.unarchiveObject(with: decodedNSData as Data) as? [String : MyData]? )!
      else {
        print("Failed decoding level information")
        return
    }
    self.c = v

  }


  func saveSettings()
  {
    let userDefaults = UserDefaults.standard

    userDefaults.set(self.a, forKey: “A”)
    userDefaults.set(self.b, forKey: “B”)
    userDefaults.set(NSKeyedArchiver.archivedData(withRootObject: self.c), forKey: “C”)
    userDefaults.synchronize()
  }

有人可以让我知道我做错了什么吗？

谢谢

Answer 1

如果您的结构实现可编码，那么您最好使用 JSONEncoder 和 JSONDecoder

struct Language: Codable {
var name: String
var version: Int
}

 let swift = Language(name: "Swift", version: 4)
 let encoder = JSONEncoder()
 if let encoded = try? encoder.encode(swift) {
// save `encoded` somewhere
}

if let encoded = try? encoder.encode(swift) {
if let json = String(data: encoded, encoding: .utf8) {
   print(json)
}

let decoder = JSONDecoder()
 if let decoded = try? decoder.decode(Language.self, from: encoded) {
    print(decoded.name)
 }