将自定义对象转换为要保存在 NSUserDefaults 中的数据

Question

我们有一个像这样的自定义对象设置：

struct BallPark: Codable,Equatable  {
    static func == (lhs: LeanVenue, rhs: LeanVenue) -> Bool {
        return lhs.id == rhs.id
    }
    let id: String
    let name: String?
    let location: VenueCoordinates?
    let mapEnabled: Bool?
    let facilityStatus: String?
    }

struct VenueCoordinates: Codable {
    let latitude: String?
    let longitude: String?
    
    var lat: Double? {
        guard let latitud = latitude else { return nil}
        return Double(latitud)
    }
    var lon: Double? {
        guard let longitude = longitude else { return nil}
        return Double(longitude)
    }
}

我们正在尝试将其转换为数据类型，以便可以将其保存为用户默认值，如下所示：

guard let bestBallParkToSave = theBestBallPark // this is of type BallPark, after fetching data

其他{return}

 let encodedBestBallPark = NSKeyedArchiver.archivedData(withRootObject: bestBallParkToSave)
            
 UserDefaults.standard.set(encodedBestBallPark, forKey: "favoriteBallPark")

问题是它在尝试转换时导致错误：

'NSInvalidArgumentException', reason: '-[__SwiftValue encodeWithCoder:]: unrecognized selector sent to instance 0x6000027dca80'

我试过使用这个堆栈溢出答案：How to convert custom object to Data Swift 但除了确保它符合 Codable 之外并没有真正明确的答案，我相信我的结构和其中的所有内容都是如此。如果您有任何建议，请告诉我。

Answer 1

那里的问题。是您将 Codable 与 NSCoding 混淆了。要使用 NSKeyedArchiver 的 archivedData 方法，您需要有一个符合 NSCoding 的 class。在你的情况下，你有一个符合 Codable 的结构，所以你需要使用 JSONEncoder encode 方法。注意：你的 equatable 方法声明是错误的：

struct BallPark: Codable, Equatable  {
    static func == (lhs: Self, rhs: Self) -> Bool {
        return lhs.id == rhs.id
    }
    let id: String
    let name: String?
    let location: VenueCoordinates?
    let mapEnabled: Bool?
    let facilityStatus: String?
}

struct VenueCoordinates: Codable {
    let latitude: String?
    let longitude: String?
    
    var lat: Double? {
        guard let latitud = latitude else { return nil}
        return Double(latitud)
    }
    var lon: Double? {
        guard let longitude = longitude else { return nil}
        return Double(longitude)
    }
}

let bestBallParkToSave = BallPark.init(id: "1", name: "Steve", location: .init(latitude: "20.0", longitude: "40.0"), mapEnabled: true, facilityStatus: "a status")

do {
    let encodedBestBallPark = try JSONEncoder().encode(bestBallParkToSave)
    UserDefaults.standard.set(encodedBestBallPark, forKey: "favoriteBallPark")
    if let ballParkData = UserDefaults.standard.data(forKey: "favoriteBallPark") {
        let loadedBallPark = try JSONDecoder().decode(BallPark.self, from: ballParkData)
        print(loadedBallPark)  // BallPark(id: "1", name: Optional("Steve"), location: Optional(VenueCoordinates(latitude: Optional("20.0"), longitude: Optional("40.0"))), mapEnabled: Optional(true), facilityStatus: Optional("a status"))
    }
} catch {
     print(error)
}

您还可以让您的生活更轻松地扩展 UserDefaults 并创建自定义编码和解码方法：

extension UserDefaults {
    func decodeObject<T: Decodable>(forKey defaultName: String, using decoder: JSONDecoder = .init()) throws -> T {
        try decoder.decode(T.self, from: data(forKey: defaultName) ?? .init())
    }
    func encode<T: Encodable>(_ value: T, forKey defaultName: String, using encoder: JSONEncoder = .init()) throws {
        try set(encoder.encode(value), forKey: defaultName)
    }
}

用法：

let bestBallParkToSave = BallPark(id: "1", name: "Steve", location: .init(latitude: "20.0", longitude: "40.0"), mapEnabled: true, facilityStatus: "a status")
do {

    try UserDefaults.standard.encode(bestBallParkToSave, forKey: "favoriteBallPark")
    let loadedBallPark: BallPark = try UserDefaults.standard.decodeObject(forKey: "favoriteBallPark")
    print(loadedBallPark)  // BallPark(id: "1", name: Optional("Steve"), location: Optional(VenueCoordinates(latitude: Optional("20.0"), longitude: Optional("40.0"))), mapEnabled: Optional(true), facilityStatus: Optional("a status"))
    
} catch {
     print(error)
}

将自定义对象转换为要保存在 NSUserDefaults 中的数据

Convert a custom object to Data to be saved in NSUserDefauts

nsuserdefaults

nskeyedarchiver

nsdata

swift

userdefaults