Swift - 使用UserDefaults来进行本地数据存储

 

1，下面通过一个样例演示UserDefaults的用法：

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        print("用户uuid：\(get_uuid())")
    }
    
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }
}

func get_uuid() -> String{
    let userid = UserDefaults.standard.string(forKey: "hangge")
    //判断UserDefaults中是否已经存在
    if(userid != nil){
        return userid!
    }else{
        //不存在则生成一个新的并保存
        let uuid_ref = CFUUIDCreate(nil)
        let uuid_string_ref = CFUUIDCreateString(nil , uuid_ref)
        let uuid = uuid_string_ref as! String
        UserDefaults.standard.set(uuid, forKey: "hangge")
        return uuid
    }
}

执行结果如下：

2，对原生数据类型的储存和读取

let userDefault = UserDefaults.standard

//Any
userDefault.set("hangge.com", forKey: "Object")
let objectValue:Any? = userDefault.object(forKey: "Object")

//Int类型
userDefault.set(12345, forKey: "Int")
let intValue = userDefault.integer(forKey: "Int")

//Float类型
userDefault.set(3.2, forKey: "Float")
let floatValue = userDefault.float(forKey: "Float")

//Double类型
userDefault.set(5.2240, forKey: "Double")
let doubleValue = userDefault.double(forKey: "Double")

//Bool类型
userDefault.set(true, forKey: "Bool")
let boolValue = userDefault.bool(forKey: "Bool")

//URL类型
userDefault.set(URL(string:"http://hangge.com")!, forKey: "URL")
let urlValue = userDefault.url(forKey: "URL")

//String类型
userDefault.set("hangge.com", forKey: "String")
let stringValue = userDefault.string(forKey: "String")

//NSNumber类型
var number = NSNumber(value:22)
userDefault.set(number, forKey: "NSNumber")
number = userDefault.object(forKey: "NSNumber") as! NSNumber

//Array类型
var array:Array = ["123","456"]
userDefault.set(array, forKey: "Array")
array = userDefault.array(forKey: "Array") as! [String]

//Dictionary类型
var dictionary = ["1":"hangge.com"]
userDefault.set(dictionary, forKey: "Dictionary")
dictionary = userDefault.dictionary(forKey: "Dictionary") as! [String : String]

3，系统对象的存储与读取

系统对象实现存储，需要通过 archivedData 方法转换成 Data 为载体，才可以存储。下面以 UILabel 对象为例：

let userDefault = UserDefaults.standard

//UILabel对象存储
//将对象转换成Data流
let label = UILabel()
label.text = "欢迎访问hangge.com"
let labelData = NSKeyedArchiver.archivedData(withRootObject: label)
//存储Data对象
userDefault.set(labelData, forKey: "labelData")

//UILabel对象读取
//获取Data
let objData = userDefault.data(forKey: "labelData")
//还原对象
let myLabel = NSKeyedUnarchiver.unarchiveObject(with: objData!) as? UILabel
print(myLabel)

对于 UIImage 对象的存储比较特殊。注意下方高亮部分，如果我们过直接把 image1 存储起来，再取出转换回 UIImage 就变成了 nil。必须先转成 image2 再存储。

let userDefault = UserDefaults.standard

//UIImage对象存储
//将对象转换成Data流
let image1 = UIImage(named: "apple.png")!
let image2 = UIImage(cgImage: image1.cgImage!, scale: image1.scale,
                     orientation: image1.imageOrientation)
let imageData = NSKeyedArchiver.archivedData(withRootObject: image2)
//存储Data对象
userDefault.set(imageData, forKey: "imageData")

//UIImage对象读取
//获取Data
let objData = userDefault.data(forKey: "imageData")
//还原对象
let myImage = NSKeyedUnarchiver.unarchiveObject(with: objData!) as? UIImage
print(myImage)

4，自定义对象的存储和读取

如果想要存储自己定义的类，首先需要对该类实现 NSCoding 协议来进行归档和反归档（序列化和反序列化）。即该类内添加 func encode(with coder: NSCoder) 方法和 init(coder decoder: NSCoder) 方法，将属性进行转换。

let userDefault = UserDefaults.standard

//自定义对象存储
let model = UserInfo(name: "航歌", phone: "3525")
//实例对象转换成Data
let modelData = NSKeyedArchiver.archivedData(withRootObject: model)
//存储Data对象
userDefault.set(modelData, forKey: "myModel")

//自定义对象读取
let myModelData = userDefault.data(forKey: "myModel")
let myModel = NSKeyedUnarchiver.unarchiveObject(with: myModelData!) as! UserInfo
print(myModel)

//----- 自定义对象类 -----
class UserInfo: NSObject, NSCoding {
    var name:String
    var phone:String
    
    //构造方法
    required init(name:String="", phone:String="") {
        self.name = name
        self.phone = phone
    }
    
    //从object解析回来
    required init(coder decoder: NSCoder) {
        self.name = decoder.decodeObject(forKey: "Name") as? String ?? ""
        self.phone = decoder.decodeObject(forKey: "Phone") as? String ?? ""
    }
    
    //编码成object
    func encode(with coder: NSCoder) {
        coder.encode(name, forKey:"Name")
        coder.encode(phone, forKey:"Phone")
    }
}

5，删除存储对象

通过 removeObject() 方法可以删除已保存的数据。当然如果这个存储对象不存在也不会报错。

UserDefaults.standard.removeObject(forKey: "hangge")