为什么在执行 NSCoding 时无法保存对类变量的更改

Question

这是我试图用nsencoding编码的自定义类的代码。变量Currensless不会初始化。

class UserData: NSObject, NSCoding {
    var race: [String]
    var religion: [String]
    var sexualOrientation: [String]
    var gender: [String]
    var currentLesson: Int
    static let DocumentsDirectory = FileManager().urls(for: .documentDirectory, in: .userDomainMask).first!
    static let ArchiveURL = DocumentsDirectory.appendingPathComponent("user")
    struct PropertyKey {
        static let nameKey = "name"
        static let race = "race"
        static let religion = "religion"
        static let sexualOrientation = "sexualOrientation"
        static let gender = "gender"
        static let currentLesson = "currentLesson"
    }
    init?(raceArray: [String], religionArray: [String], sexualOrientationArray: [String], genderArray: [String]) {
        self.race = raceArray
        self.religion = religionArray
        self.sexualOrientation = sexualOrientationArray
        self.gender = genderArray
        self.currentLesson = 0
        super.init()
    }
    // NSCoding
    func encode(with aCoder: NSCoder) {
        aCoder.encode(race, forKey: PropertyKey.race)
        aCoder.encode(religion, forKey: PropertyKey.religion)
        aCoder.encode(sexualOrientation, forKey: PropertyKey.sexualOrientation)
        aCoder.encode(gender, forKey: PropertyKey.gender)
        aCoder.encode(currentLesson, forKey: PropertyKey.currentLesson)
    }
    required convenience init?(coder aDecoder: NSCoder) {
        let race = aDecoder.decodeObject(forKey: PropertyKey.race) as! [String]
        let religion = aDecoder.decodeObject(forKey: PropertyKey.religion) as! [String]
        let sexualOrientation = aDecoder.decodeObject(forKey: PropertyKey.sexualOrientation) as! [String]
        let gender = aDecoder.decodeObject(forKey: PropertyKey.gender) as! [String]
        self.init(raceArray: race, religionArray: religion, sexualOrientationArray: sexualOrientation, genderArray: gender)
    }
}

现在，这是我尝试更改Curterless变量的代码：

let user = NSKeyedUnarchiver.unarchiveObject(withFile: UserData.ArchiveURL.path) as? UserData
print(user!.currentLesson)
user?.currentLesson = 1
print(user!.currentLesson)
NSKeyedArchiver.archiveRootObject(user!, toFile: UserData.ArchiveURL.path)
let user2 = NSKeyedUnarchiver.unarchiveObject(withFile: UserData.ArchiveURL.path) as? UserData
print(user2!.currentLesson)

但是，正如我可以从打印语句(0/n 1/n 0(中看到的那样，Curressless var不会更新。为什么是这样？我很困惑如何更改它并保存它而不是初始化值之一。

Answer 1

您编码currentLesson，但您不解码。您没有尝试在init(coder:)初始化器中获取编码值。因此，当您调用其他init时，它将重置回0。

您需要更新init方法。以下内容应起作用(请注意新的currentLesson参数的默认值(：

init?(raceArray: [String], religionArray: [String], sexualOrientationArray: [String], genderArray: [String], currentLesson: Int = 0) {
    self.race = raceArray
    self.religion = religionArray
    self.sexualOrientation = sexualOrientationArray
    self.gender = genderArray
    self.currentLesson = currentLesson
    super.init()
}
required convenience init?(coder aDecoder: NSCoder) {
    let race = aDecoder.decodeObject(forKey: PropertyKey.race) as! [String]
    let religion = aDecoder.decodeObject(forKey: PropertyKey.religion) as! [String]
    let sexualOrientation = aDecoder.decodeObject(forKey: PropertyKey.sexualOrientation) as! [String]
    let gender = aDecoder.decodeObject(forKey: PropertyKey.gender) as! [String]
    let currentLesson = aDecoder.decodeInteger(forKey: PropertyKey.currentLesson)
    self.init(raceArray: race, religionArray: religion, sexualOrientationArray: sexualOrientation, genderArray: gender, currentLesson: currentLesson)
}