Swift 3从userDefaults保存和检索自定义对象

问题描述

我在Playground中使用Swift 3，Xcode 8.0:

I have this in Playground using Swift 3, Xcode 8.0:

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")
    }
}

---

创建人员数组

---

create array of Person

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

---

编码数组

---

encode the array

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

---

保存为userDefaults

---

save to userDefaults

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

---

检查

---

check

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

---

从userDefaults撤消

---

retreive from userDefaults

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

---

只需检查已存档的数据

---

just check the archived data

if let myPeopleList = NSKeyedUnarchiver.unarchiveObject(with: encodedData){
   print("myPeopleList: \(myPeopleList)")
}else{
   print("There is an issue")
}

我无法正确地将数据对象保存为userDefaults，此外，底部的检查还会产生错误严重错误:在解开Optional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?

I'm not able to correctly save the data object to userDefaults, and in addition, the check at the bottom creates the error "fatal error: unexpectedly found nil while unwrapping an Optional value". The "check" line also shows the saved object is nil. Is this an error in my object's NSCoder?

推荐答案

Swift 4或更高版本

您可以再次在Playground中保存/测试您的值

You can once again save/test your values in a Playground

UserDefaults需要在真实项目中进行测试.注意:无需强制同步.如果要在运动场中测试编码/解码，则可以使用键控存档器将数据保存到文档目录中的plist文件中.您还需要修复班级中的一些问题:

UserDefaults need to be tested in a real project. Note: No need to force synchronize. If you want to test the coding/decoding in a playground you can save the data to a plist file in the document directory using the keyed archiver. You need also to fix some issues in your class:

class Person: NSObject, NSCoding {
    let name: String
    let age: Int
    init(name: String, age: Int) {
        self.name = name
        self.age = age
    }
    required init(coder decoder: NSCoder) {
        self.name = decoder.decodeObject(forKey: "name") as? String ?? ""
        self.age = decoder.decodeInteger(forKey: "age")
    }

    func encode(with coder: NSCoder) {
        coder.encode(name, forKey: "name")
        coder.encode(age, forKey: "age")
    }
}

测试:

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        // setting a value for a key
        do {
            let newPerson = Person(name: "Joe", age: 10)
            var people = [Person]()
            people.append(newPerson)
            let encodedData = try NSKeyedArchiver.archivedData(withRootObject: people, requiringSecureCoding: false)
            UserDefaults.standard.set(encodedData, forKey: "people")

        } catch {
            print(error)
        }

        // retrieving a value for a key
        do {
            if let data = UserDefaults.standard.data(forKey: "people"),
                let myPeopleList = try NSKeyedUnarchiver.unarchiveTopLevelObjectWithData(data) as? [Person] {
                myPeopleList.forEach({print( $0.name, $0.age)})  // Joe 10
            } else {
                print("There is an issue")
            }
        } catch {
            print(error)
        }
    }
}

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