Swift - 使用 Codeable 保存对象会导致应用程序崩溃

Question

我正在编写一个应用程序，我试图通过 Codable 将数组保存在数组中并保存到 UserDefaults，但它崩溃了，并出现以下错误：

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[Here.UserEntries encodeWithCoder:]: unrecognized selector sent to instance 0x600000649e70'

我是这样保存的：

class UserEntries: NSObject, Codable {
    struct Question : Codable {
        var question: String
        var answer: String

        enum CodingKeys: String, CodingKey {
            case question
            case answer
        }

        init(question: String, answer: String) {
            self.question = question
            self.answer = answer
        }
        func encode(to encoder: Encoder) throws {
            var container = encoder.container(keyedBy: CodingKeys.self)
            try container.encode(question, forKey: .question)
            try container.encode(answer, forKey: .answer)
        }
        init(from decoder: Decoder) throws {
            let container = try decoder.container(keyedBy: CodingKeys.self)
            question = try container.decode(String.self, forKey: .question)
            answer = try container.decode(String.self, forKey: .answer)
        }
    }

    var date: String
    var questions: [Question]

    enum CodingKeys: String, CodingKey {
        case date
        case questions
    }

    init(date: String, questions: [Question]) {
        self.date = date
        self.questions = questions
    }

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

    required init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        date = try container.decode(String.self, forKey: .date)
        questions = [try container.decode(Question.self, forKey: .questions)]
    }
}

其中 userEntry 是：

let userEntry = UserEntries(date: String(todayDate), questions: [UserEntries.Question(question: q1Text, answer: q1Answer), UserEntries.Question(question: q2Text, answer: q2Answer)])

然后

UserDefaults.standard.set(NSKeyedArchiver.archivedData(withRootObject: userEntry), forKey: "allEntries")

到底出了什么问题？我有一种感觉，我不能在数组中保存一个数组，但是这怎么能解决呢？

Answer 1

要将模型设置为 UserDefaults 请试试这个

 if let encoded = try? JSONEncoder().encode(value) {
    UserDefaults.standard.set(encoded, forKey: "allEntries")
 }

用于解码：

if let data = UserDefaults.standard.value(forKey: "allEntries") as? Data {
    if let yourData = try? JSONDecoder().decode(UserEntries.self, from: data) {
        Print(yourData) 
    }
}

Answer 2

这一行：

questions = [try container.decode(Question.self, forKey: .questions)]

不正确。要获得 Question 的数组，您应该解码数组的类型 [Question].self:

questions = try container.decode([Question].self, forKey: .questions)

另外，请注意 Decodable/Encodable 与 JSONDecoder/JSONEncoder 一起使用，请参阅 official docs。根据这个，这里是你需要保存的（编码为数据然后保存）：

let jsonEncoder = JSONEncoder()
if let value = try? jsonEncoder.encode(userEntry) {
    UserDefaults.standard.set(value, forKey: "allEntries")
}

相反 - 获取数据，如果是，则尝试解码对象：

let jsonDecoder = JSONDecoder()
if let data = UserDefaults.standard.data(forKey: "allEntries"),
   let userEntry = try? jsonDecoder.decode(UserEntries.self, from: data) {

   // here you get userEntry
}

示例：

let userEntry = UserEntries(date: "1 Sep 18",
    questions: [
        UserEntries.Question(question: "q1Text", answer: "q1Answer"),
        UserEntries.Question(question: "q2Text", answer: "q2Answer")
    ])

let jsonEncoder = JSONEncoder()
if let value = try? jsonEncoder.encode(userEntry) {
    UserDefaults.standard.set(value, forKey: "allEntries")
}

let jsonDecoder = JSONDecoder()
if let data = UserDefaults.standard.data(forKey: "allEntries"),
    let userEntry = try? jsonDecoder.decode(UserEntries.self, from: data) {

    print(userEntry.date) // 1 Sep 18
}

Swift - 使用 Codeable 保存对象会导致应用程序崩溃

Swift - Saving an Object with Codeable crashes app

ios

save

swift4

nsuserdefaults

codable