swift--使用UserDefaults来进行本地数据存储
UserDefaults适合轻量级的本地客户端存储，存储一个值，新值可以覆盖旧值，可以重复存储，也可以存储一次，然后直接从UserDefaults里面读取上次存储的信息，很方便，用的时候，宏定义下，直接调用！
轻量级数据库的话，移动端一般使用SQlite数据库，也是一款轻量级的适合移动端设备的数据库，具体可以参考我以前写的关于SQlite的博客，当然了UserDefaults根本不用管这些东西，直接就想读取字符串一样，直接读取就可以了！
UserDefaults支持的数据格式也很多：有：Int，Float，Double，BOOL，Array，Dictionary，甚至 Any 类型
1. 样例展示：
func get_uuid() -> String {
let userID = UserDefaults.standard.string(forKey: "HHGGLL") //判断UserDefaults中是否已经存在
if userID != nil { return userID!
}else{
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: "HHGGLL") return uuid
}
}输出：
print("用户的UUID：(get_uuid())")
如上图！
2.其他基本数据类型和any类型的存储
//存储练习
let userDefault = UserDefaults.standard //any
userDefault.set("hgl001", forKey: "object")
let objectValue:Any? = userDefault.object(forKey: "object")
print("(objectValue as! String)") //int
userDefault.set(12345, forKey: "int")
let intValue = userDefault.integer(forKey: "int")
print(intValue) //float
userDefault.set(3.2, forKey: "float")
let floatValue = userDefault.float(forKey: "float")
print(floatValue) //double
userDefault.set(5.2369, forKey: "double")
let doubleValue = userDefault.double(forKey: "double")
print(doubleValue) //bool
userDefault.set(true, forKey: "bool")
let boolValue = userDefault.bool(forKey: "bool")
print(boolValue) //url
userDefault.set(URL(string:"http://hangge.com")!, forKey: "URL")
let urlValue = userDefault.url(forKey: "URL")
print(urlValue) //string类型
userDefault.set("hgl is a hero!", forKey: "string")
let stringValue = userDefault.string(forKey: "string")
print(stringValue) //nsnumber类型
var number = NSNumber(value:22)
userDefault.set(number, forKey: "number")
number = userDefault.object(forKey: "number") as! NSNumber
print(number) //array类型
var array:Array = ["123","223"]
userDefault.set(array, forKey: "Array")
array = userDefault.array(forKey: "Array") as! [String]
print(array) //Dictionary类型
var dictory = ["name":"hero11223"]
userDefault.set(dictory, forKey: "dictory")
dictory = userDefault.dictionary(forKey: "dictory") as! [String:String]
print(dictory) //系统对象的存储与读取
let userDeafaults = UserDefaults.standard //存储对象
let label = UILabel()
label.text = "天空飘来五个字"
let labelData = NSKeyedArchiver.archivedData(withRootObject: label) //存储data对象
userDefault.set(labelData, forKey: "labelData")
//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) //UIImage对象存储
let image1 = UIImage(named:"1.jpeg")
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 objDatas = userDefault.data(forKey: "imageData") //还原对象
let myImg = NSKeyedUnarchiver.unarchiveObject(with: objDatas!)
print("输出是(myImg)")打印如下图：
3.删除存储对象
通过removeObject()方法可以删除已保存的数据
UserDefaults.standard.removeObject(forKey: "key值")