快速从 UserDefaults 保存和检索自定义对象 [英] Swift saving and retrieving custom object from UserDefaults

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")
    }
}

---

创建人的数组

---

create array of Person

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

---

对数组进行编码

---

encode the array

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

---

保存到用户默认值

---

save to userDefaults

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

---

检查

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

---

从 userDefaults 中检索

---

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")
}

---

只需检查存档数据

---

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到 userDefaults，此外，底部的检查创建了错误:

I'm not able to correctly save the data object to userDefaults, and in addition, the check at the bottom creates the error:

致命错误:在展开可选值时意外发现 nil

Fatal error: Unexpectedly found nil while unwrapping an Optional value

检查"行还显示保存的对象为零.这是我对象的 NSCoder 中的错误吗?

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 需要在实际项目中进行测试.注意:无需强制同步.如果您想在操场上测试编码/解码，您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.您还需要解决班级中的一些问题:

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:

---

Testing:

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()

        do {
            // setting a value for a key
            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")
            // retrieving a value for a key
            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
            }                    
        } catch {
            print(error)
        }
        
    }
}

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