【iOS数据持久化】归档解档（NSKeyedArchiver/ NSKeyedUnarchiver）

简介

归档（Archive）也称为序列化（serialization）,把对象转化为字节码，以文件的形式存储在磁盘上，只要遵循了NSCoding协议的对象都可以实现归档和解档（大部分foundation和Cocoa Touch类都可以），将文档上的字节码转化为对象的过程叫做解档（unarchive）也叫反序列化（unserialization）

归档的数据类型要求; NSData、NSString、NSNumber、NSDate、NSArray、NSDictionary五种类型，如果不能归档，我们可以尝试转化为这五种中的任何一种再进行存储

单个对象归档解档

//获取归档文件路径
NSString *documentPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES).lastObject;
NSString *filePath = [documentPath stringByAppendingPathComponent:@"test"];//对字符串@”test”进行归档，写入到filePath中
[NSKeyedArchiver archiveRootObject:@"test" toFile:filePath];//根据保存数据的路径filePath解档数据
NSString *result = [NSKeyedUnarchiver unarchiveObjectWithFile:filePath];
//log结构为@”test”，就是上面归档的数据
NSLog(@"%@",result);

归档基本数据或基本对象，框架内定义的（或者已经遵守NSCoding协议的自定义类）中的单个对象进行归档解档（一次只能归档一个，多个需要分开多次归档）

多个对象归档解档

    //获取归档路径NSString *documentPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES).lastObject;NSString *filePath = [documentPath stringByAppendingPathComponent:@"test"];//用来承载数据的NSMutableDataNSMutableData *data = [[NSMutableData alloc] init];//归档对象NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];//将要被保存的三个数据NSString *name = @"jack";int age = 17;double height = 1.78;//运用encodeObject:方法归档数据[archiver encodeObject:name forKey:@"name"];[archiver encodeInt:age forKey:@"age"];[archiver encodeDouble:height forKey:@"height"];//结束归档[archiver finishEncoding];//写入数据（存储数据）[data writeToFile:filePath atomically:YES];//NSMutableData用来承载解档出来的数据NSMutableData *resultData = [[NSMutableData alloc] initWithContentsOfFile:filePath];//解档对象NSKeyedUnarchiver *unArchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:resultData];//分别解档出三个数据NSString *resultName = [unArchiver decodeObjectForKey:@"name"];int resultAge = [unArchiver decodeIntForKey:@"age"];double resultHeight = [unArchiver decodeDoubleForKey:@"height"];//结束解档[unArchiver finishDecoding];//成功打印出结果，说明成功归档解档NSLog(@"name = %@, age = %d, height = %.2f",resultName,resultAge,resultHeight);

自定义对象的归档解档，

只需要在自定义类里遵循NSSecureCoding(NSCoding iOS 12后删除)协议，而且必须实现归档方法(encodeWithCoder(aCoder:NSCoder))和解档方法（init?(coder aDecoder: NSCoder)）

自定义对象遵循和继承NSObject

class Student:NSObject, NSSecureCoding {var name: String = ""var teacher: String = ""var age: Int = 0var isMale: Bool = falsestatic var supportsSecureCoding: Bool = trueoverride init() {super.init() }func encode(with coder: NSCoder) {coder.encode(name, forKey: "name")coder.encode(teacher, forKey: "teacher")coder.encode(age, forKey: "age")coder.encode(isMale, forKey: "isMale")}required init?(coder: NSCoder) {self.name = coder.decodeObject(forKey: "name") as! Stringself.teacher = coder.decodeObject(forKey: "teacher") as! Stringself.age = Int(coder.decodeInt32(forKey: "age"))self.isMale =  coder.decodeBool(forKey: "isMale")}
}

归档

let archiverPath = NSHomeDirectory() + "/Documents/xiaohongInfo.plist"private func archiverStudent() {let xiaohong = Student()xiaohong.name = "小红"xiaohong.age = 19xiaohong.isMale = truexiaohong.teacher = "Mrs.Yang"print(archiverPath)do {let data = try NSKeyedArchiver.archivedData(withRootObject: xiaohong, requiringSecureCoding: true)try data.write(to: URL(fileURLWithPath: archiverPath))} catch (let err) {print(err)}}

解档

private func unarchiverStudent() {do {let data = try Data(contentsOf: URL(fileURLWithPath: archiverPath))let xiaohong = try NSKeyedUnarchiver.unarchiveTopLevelObjectWithData(data) as! Studentprint(xiaohong)} catch let error {print(error)}}