好吧,在这里调查了几个类似的主题,按照建议完成了所有操作,但是我的计算属性"previousUserData"在尝试将解码的对象转换为我的类型时返回nil。怎么了?
@objc class PreviousUserData: NSObject, NSCoding {
var name: String
var phone: String
var email: String
func encode(with aCoder: NSCoder) {
aCoder.encode(name, forKey: "name")
aCoder.encode(phone, forKey: "phone")
aCoder.encode(email, forKey: "email")
}
required convenience init?(coder aDecoder: NSCoder) {
guard
let name = aDecoder.decodeObject(forKey: "name") as? String,
let phone = aDecoder.decodeObject(forKey: "phone") as? String,
let email = aDecoder.decodeObject(forKey: "email") as? String
else {
return nil
}
self.init(name: name, phone: phone, email: email)
}
init(name: String, phone: String, email: String) {
self.name = name
self.phone = phone
self.email = email
}
}
未存档返回我 nil,但存在关键"用户数据"的数据
var previousUserData: PreviousUserData? {
get {
if let object = UserDefaults.standard.object(forKey: "userdata") as? Data {
let unarchived = NSKeyedUnarchiver.unarchiveObject(with: object) as? PreviousUserData
return unarchived
}
return nil
}
set {
let encodedData: Data = NSKeyedArchiver.archivedData(withRootObject: previousUserData as Any)
UserDefaults.standard.setValue(encodedData, forKey: "userdata")
}
}
实际上,
您无法获得有效数据,因为二传手是错误的。你必须保存newValue
而不是previousUserData
.
这是一个稍微优化的版本
var previousUserData: PreviousUserData? {
get {
guard let data = UserDefaults.standard.data(forKey: "userdata") else { return nil }
return NSKeyedUnarchiver.unarchiveObject(with: data) as? PreviousUserData
}
set {
guard let newValue = newValue else { return }
let encodedData = NSKeyedArchiver.archivedData(withRootObject: newValue)
UserDefaults.standard.set(encodedData, forKey: "userdata")
}
}
NSCoding
很重。在这种情况下,我建议使用 Codable
将数据序列化为 JSON 或属性列表。它摆脱了@objc
、class
和NSObject
,并将整个代码减少到
struct PreviousUserData : Codable {
var name: String
var phone: String
var email: String
}
var previousUserData: PreviousUserData? {
get {
guard let data = UserDefaults.standard.data(forKey: "userdata") else { return nil }
return try? JSONDecoder().decode(PreviousUserData.self, from: data)
}
set {
guard let newValue = newValue, let encodedData = try? JSONEncoder().encode(newValue) else { return }
UserDefaults.standard.set(encodedData, forKey: "userdata")
}
}