iOS 数据持久化方式 - 归档 反归档

• 所谓归档:将复杂对象转化为NSData类型数据(复杂-->归档-->NSData--->WriteToFile)
  注意:归档是将对象转化为数据字节,以文件的形式存储在磁盘上,

• 所谓反归档:将NSData类型数据转化为复杂对象(读取文件-->NSData-->反归档--->复杂对象)

  ---

  再说归档之前,先说下iOS的数据持久化方式:
  那么问题来了,什么是数据持久化?

  数据持久化(侠义的理解):仅仅指把域对象永久保存到数据库中,(广义的理解):包括和数据库相关的各种操作
  优点:
  1:数据持久化可以减少访问数据库数据的次数,增加应用程序执行的速度;
  2:代码重用性高,能够完成大部分数据库操作;
  3:低耦合,使持久化不依赖于底层数据库和上层业务逻辑实现,更换数据库时只需要修改配置文件而不用修改代码

那么iOS的数据化持久方式有哪些呢?

1:属性列表(Plist文件),NSUserDefault
2:归档(NSKeyedArchiver)
3:数据库(SQlite,CoreData,FMDB(第三方))

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今天重点说下归档和结档的问题
归档的三种方式:

1:对foundation框架的对象进行归档
2:对自定义的对象进行归档
3:对自定义内容进行归档
注意:归档生成的文件是加密的

---

下边举简单的例子分别说下归档的三种方式

#pragma mark---对自定义对象进行归档反归档----
- (void)archive{
//先创建一个Person类
/*
 第一:复杂对象所属的类一定要遵循NSCoding协议
 第二:实现协议中的方法
 - (void)encodeWithCoder:(NSCoder *)aCoder;
 - (instancetype)initWithCoder:(NSCoder *)aDecoder;
//归档(由叫序列化)的步骤
//对Person类对象进行归档时执行此方法.并对Person类中想要进行归档的所有属性,进行序列化操作

- (void)encodeWithCoder:(NSCoder *)aCoder{
    [aCoder encodeObject:_name forKey:@"name"];
    [aCoder encodeObject:_gender forKey:@"gender"];
    [aCoder encodeObject:_age forKey:@"age"];
}

//反归档(由叫反序列化)的步骤
//对Person类对象进行反归档时执行此方法.并对Person类中想要进行反归档的所有属性,进行反序列化操作
- (instancetype)initWithCoder:(NSCoder *)aDecoder{
    if (self = [super init]) {
        _name = [aDecoder decodeObjectForKey:@"name"];
        _gender = [aDecoder decodeObjectForKey:@"gender"];
        _age = [aDecoder decodeObjectForKey:@"age"];
    }
        return self;

}

 */

    person *per = [person new];
    per.name = @"甲甲";
    per.age = @"20";
    per.gender = @"女";

    //归档
    //1:准备路径
    NSString *path = NSHomeDirectory();
    path = [path stringByAppendingString:@"Singel.plist"];
    //2:准备存储数据对象(用可变数组进行接收)
    NSMutableData *data = [NSMutableData new];
    //3:创建归档对象
    NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc]initForWritingWithMutableData:data];
    //4:开始归档
    [archiver encodeObject:per forKey:@"person"];
    //5:完成归档
    [archiver finishEncoding];
    //6:写入文件
    BOOL result = [data writeToFile:path atomically:YES];
    if (result) {
        NSLog(@"归档成功:%@",path);
    }

    //反归档
    //1:获取解档路径
    NSData *MyData = [NSData dataWithContentsOfFile:path];
    //2:创建反归档对象
    NSKeyedUnarchiver  *unarchiver= [[NSKeyedUnarchiver alloc]initForReadingWithData:MyData];
    //3:反归档
    person *aper = [person new];
    aper = [unarchiver decodeObjectForKey:@"person"];
    //4:结束归档
    [unarchiver finishDecoding];
    NSLog(@"%@",aper.name);
}

#pragma mark----对foundation框架中的对象进行归档和反归档
- (void)fundationClass{
//归档
    //1:创建路径
    NSString *Doucuments = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)firstObject];
    NSString *path = [Doucuments stringByAppendingString:@"file.plist"];
    //2:归档(不需要结束方法)
    NSArray *array = @[@"jiajia",@"jiejie",@"pangpang"];
    BOOL result = [NSKeyedArchiver archiveRootObject:array toFile:path];
    if (result) {
        NSLog(@"框架中的归档%@",path);
    }
    //反归档
    NSArray *newArray = [NSKeyedUnarchiver unarchiveObjectWithFile:path];
    NSLog(@"框架的结档%@",newArray);
}

#pragma mark----对自定义的内容进行归档和反归档
- (void)customContent{
//归档
    //1:获取路径

    NSString *path = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)firstObject];

   path = [path stringByAppendingString:@"custom.plist"];

    NSMutableData *data = [NSMutableData data];

    NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc]initForWritingWithMutableData:data];

    [archiver encodeObject:@"111" forKey:@"name"];
    [archiver encodeObject:@"2" forKey:@"gender"];
    [archiver encodeObject:@"100" forKey:@"age"];

    [archiver finishEncoding];

    BOOL result = [data writeToFile:path atomically:YES];
    if (result) {
        NSLog(@"归档%@",path);
    }
    NSData *newdata = [NSData dataWithContentsOfFile:path];
    NSKeyedUnarchiver *unkeyed =  [[NSKeyedUnarchiver alloc]initForReadingWithData:newdata];
//    NSString *str1 = [unkeyed decodeObjectForKey:@"name"];
//    NSString *str2 = [unkeyed decodeObjectForKey:@"gender"];
//    NSString *str3 = [unkeyed decodeObjectForKey:@"age"];

    person *pp = [person new];
    pp.name = [unkeyed decodeObjectForKey:@"name"];
    pp.gender = [unkeyed decodeObjectForKey:@"gender"];
    pp.age = [unkeyed decodeObjectForKey:@"age"];
    [unkeyed finishDecoding];
    NSLog(@"name:%@ gender:%@ age:%@",pp.name,pp.gender,pp.age);
//    NSLog(@"name:%@ gender:%@ age:%@",str1,str2,str3);

}