Swift 3从userDefaults保存和检索自定义对象

Question

我使用Swift 3，Xcode 8.0在Playground中拥有此功能：

import Foundation
class Person: NSObject, NSCoding {
    var name: String
    var age: Int
    init(name: String, age: Int) {
        self.name = name
        self.age = age
    }
    required convenience init(coder aDecoder: NSCoder) {
        let name = aDecoder.decodeObject(forKey: "name") as! String
        let age = aDecoder.decodeObject(forKey: "age") as! Int
        self.init(
            name: name,
            age: age
        )
    }
    func encode(with aCoder: NSCoder) {
        aCoder.encode(name, forKey: "name")
        aCoder.encode(age, forKey: "age")
    }
}

---

创建人数组

let newPerson = Person(name: "Joe", age: 10)
var people = [Person]()
people.append(newPerson)

---

编码数组

let encodedData = NSKeyedArchiver.archivedData(withRootObject: people)
print("encodedData: \(encodedData))")

---

保存到userDefaults

let userDefaults: UserDefaults = UserDefaults.standard()
userDefaults.set(encodedData, forKey: "people")
userDefaults.synchronize()

---

print("saved object: \(userDefaults.object(forKey: "people"))")

从userDefaults检索
if let data = userDefaults.object(forKey: "people") {
    let myPeopleList = NSKeyedUnarchiver.unarchiveObject(with: data as! Data)
    print("myPeopleList: \(myPeopleList)")
}else{
    print("There is an issue")
}

仅检查存档数据
if let myPeopleList = NSKeyedUnarchiver.unarchiveObject(with: encodedData){
   print("myPeopleList: \(myPeopleList)")
}else{
   print("There is an issue")
}

我无法将数据对象正确保存为userDefaults，此外，底部的检查还会产生错误“严重错误：在展开可选值时意外发现nil”。 “检查”行还显示已保存的对象为nil。这是我对象的NSCoder中的错误吗？

Answer 1

Swift 4注意

Answer 2

let age = aDecoder.decodeObject(forKey: "age") as! Int

Answer 3

尝试一下：

Answer 4

在Swift 4中：