尝试获取 nil 值时解码器崩溃也编码解码枚举值不起作用

Question

我有一个带有一些属性的 class，我在保存时使用编码，在获取时使用解码器，但有些数据不是可选的，但在我第一次获取时它是空的所以当解码器正在调用并且发现 nill 值时，它会使应用程序崩溃。

所以我想要的是当我获取数据时如果没有找到数据我可以设置一些默认值而不是崩溃我可以通过将这些属性设为可选来解决这个问题但我不想要那样。而且也无法添加 try catch 以确保它不会崩溃

请告诉我应该对此进行哪些更改class，并分享一些示例或链接或教程，深入解释有关编码器和解码器的所有内容（不是一些仅概述的媒体文章）

我是 swift 的新手，所以如果您发现此 class 有任何问题，请在评论中告诉我最新 swift

的最佳处理方式

import Foundation

enum AcModeType {
    case acModeCool
    case acModeDry
    case acModeHeat
    case acModeFan
    case acModeTimer
}

enum FanModeType {
    case fanModeLow
    case fanModeMid
    case fanModeHigh
    case FanModeAuto
}

class AcDevice: Device {
    var brandId: String?
    var variant: String?
    var brandName: String?
    var acTemperature: Int = 16
    var acMinTemperature: Int = 16
    var acMaxTemperature: Int = 32
    var weatherTemperature: Int = 0
    var roomTemperature: Int = 0
    var timeTable = [TimeTable]()
    var currentAcMode: AcModeType = .acModeCool
    var currentFanMode: FanModeType = .fanModeLow
    var lastPowerOnTime: Double = 0.0
    var isPowerOn = false
    var isSleepOn = false
    var isTimeTableOn = false
    var hasScreen = false

    required public init?(coder aDecoder: NSCoder) {
        super.init();
        brandId             =   (aDecoder.decodeObject(forKey: "brandId") as! String?)
        variant             =   (aDecoder.decodeObject(forKey: "variant") as! String?)
        brandName           =   (aDecoder.decodeObject(forKey: "brandName") as! String?)
        acTemperature       =   (aDecoder.decodeObject(forKey: "temperature") as! Int)
        acMinTemperature    =   (aDecoder.decodeObject(forKey: "acMinTemperature") as! Int )
        acMaxTemperature    =   (aDecoder.decodeObject(forKey: "acMaxTemperature") as! Int )
        weatherTemperature  =   (aDecoder.decodeObject(forKey: "weatherTemperature") as! Int)
        roomTemperature     =   (aDecoder.decodeObject(forKey: "roomTemperature") as! Int )
        currentAcMode       =   (aDecoder.decodeObject(forKey: "currentAcMode") as! AcModeType)
        currentFanMode      =   (aDecoder.decodeObject(forKey: "currentFanMode") as! FanModeType)
        lastPowerOnTime     =   (aDecoder.decodeObject(forKey: "lastPowerOnTime") as! Double)
        if let timeTable    =   aDecoder.decodeObject(forKey: "timeTable") as! [TimeTable]? {self.timeTable=timeTable}
    }

    public override func encode(with aCoder: NSCoder) {
        aCoder.encode(self.brandId, forKey: "brandId")
        aCoder.encode(self.variant, forKey: "variant")
        aCoder.encode(self.brandName, forKey: "brandName")
        aCoder.encode(self.acTemperature, forKey: "temperature")
        aCoder.encode(self.timeTable, forKey: "timeTable")
        aCoder.encode(self.acMinTemperature, forKey: "acMinTemperature")
        aCoder.encode(self.acMaxTemperature, forKey: "acMaxTemperature")
        aCoder.encode(self.weatherTemperature, forKey: "weatherTemperature")
        aCoder.encode(self.roomTemperature, forKey: "roomTemperature")
        aCoder.encode(self.currentAcMode, forKey: "currentAcMode")
        aCoder.encode(self.currentFanMode, forKey: "currentFanMode")
        aCoder.encode(self.lastPowerOnTime, forKey: "lastPowerOnTime")
    }

    required public init() {
        super.init();
        brandId = ""
        variant = ""
        brandName = ""

        isPowerOn = false;
        isSleepOn = false;
        isTimeTableOn = false;
        hasScreen = false;
        currentAcMode = .acModeCool
        acMinTemperature = 16;
        acMaxTemperature = 32;
        currentFanMode = .fanModeLow
        lastPowerOnTime = -1;
        timeTable = [TimeTable]()
    }
}

Answer 1

在您的 required public init?(coder aDecoder: NSCoder) 中，您正在使用 as! 强制转换 decodeObject 的结果，因此如果失败，您的应用程序将崩溃。相反，您可以将 as? 与默认值结合使用来解包您的可选值。

例如：

brandId = aDecoder.decodeObject(forKey: "brandId") as? String ?? "your default string"

这使用 ??，它是 nil 合并运算符，当左侧为 nil 时提供默认值。

Answer 2

您可以使用 swift 中的 Codable 协议来做到这一点。看看下面的 link.

https://hackernoon.com/everything-about-codable-in-swift-4-97d0e18a2999

并且

Apple 文档：

https://developer.apple.com/documentation/foundation/archives_and_serialization/encoding_and_decoding_custom_types

尝试获取 nil 值时解码器崩溃也编码解码枚举值不起作用

aDecoder crash when try to fetch nil value also encoding decoding enum values not working

enums

encode

decode

swift

swift4