Swift 3从UserDefaults保存和检索自定义对象

小编典典

Swift 3从UserDefaults保存和检索自定义对象

swift

我在Playground中使用Swift 3，Xcode 8.0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")
    }
}

创建人员数组

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))")

保存到用户默认值

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

检查

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

从userDefaults返回

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

只需检查存档的数据

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

我无法正确将数据对象保存到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？

阅读 362

2020-07-07

共1个答案

小编典典

斯威夫特4注意

您可以再次在Playground中保存/测试您的值

迅捷3

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：

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
        let newPerson = Person(name: "Joe", age: 10)
        var people = [Person]()
        people.append(newPerson)
        let encodedData = NSKeyedArchiver.archivedData(withRootObject: people)
        UserDefaults.standard.set(encodedData, forKey: "people")

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

2020-07-07