数据存储之归档

• 归档 NSKeyedArchiver : 序列化，把对象转为字节码，存储到文件中，然后将文件存储到硬盘中，实现数据的持久化

• 解归档 NSKeyedUnarchiver: 反序列化，把字节码转为对象

注：

1. 归档Foundation框架中的对象

2. 归档自定义的对象，但是需要注意所归档的对象类必须遵守<NSCoding>协议

3. 归档之后的文件是加密的，安全性高

归档的代码实现

归档 (序列化)

归档的内容
NSArray *ary = @[@21, @"ios", @"apple", [NSDate date]];
归档的文件的路，即要存入的路径
NSString *documentPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) firstObject];
NSString *filePath = [documentPath stringByAppendingPathComponent:@"test.archiver"];
NSLog(@"%@",filePath);
归档
BOOL res = [NSKeyedArchiver archiveRootObject:ary toFile:filePath];
if (res) {
    NSLog(@"归档成功");
}

解归档 （反序列化）

id object = [NSKeyedUnarchiver unarchiveObjectWithFile:filePath];
NSLog(@"解归档： %@", object);

但是这种系统提供的归档方式太过死板，不够灵活，所以选择自定义归档方法

自定义归档方法实现

//归档文件的路径
NSString *documentPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
NSString *filePath = [documentPath stringByAppendingPathComponent:@"test.archiver"];

归档

1. 创建NSMutableData实例作为归档存储数据
NSMutableData *data = [NSMutableData data];

2. 创建归档的对象
NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];

3. 添加归档内容 （设置key、value值）
[archiver encodeObject:@"apple" forKey:@"name"];
[archiver encodeInt:21 forKey:@"age"];
[archiver encodeObject:@[@"abc",@"123"] forKey:@"ary"];

自定义的Student对象
Student *stu = [[Student alloc] init];
stu.name = @"jredu";
stu.num = 1;
[archiver encodeObject:stu forKey:@"stu"];

4. 完成归档
[archiver finishEncoding];
5. 将归档的数据存储到磁盘中
if ([data writeToFile:filePath atomically:YES]) {
    NSLog(@"归档完成");
}

解归档

1. 从磁盘读取文件，生成NSData实例
NSData *contentData = [NSData dataWithContentsOfFile:filePath];

2. 根据NSData实例创建和初始化解归档的对象
NSKeyedUnarchiver *unArchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:contentData]；

3. 解归档，根据key值获取value值
NSString *name = [unArchiver decodeObjectForKey:@"name"];
int age = [unArchiver decodeIntForKey:@"age"];
id ary = [unArchiver decodeObjectForKey:@"ary"];
NSLog(@"%@  %i  %@",name, age, ary);

Student *unArchiverStu = [unArchiver decodeObjectForKey:@"stu"];
NSLog(@"name:%@  num:%i",unArchiverStu.name, unArchiverStu.num);

对于自定义的对象的归档，需要注意所归档的对象类必须遵守<NSCoding>协议

#pragma mark - 编码：对对象的属性进行编码
-(void)encodeWithCoder:(NSCoder *)aCoder{
[aCoder encodeInt:_num forKey:@"num"];
[aCoder encodeObject:_name forKey:@"name"];
}

#pragma mark - 解码：解码归档数据初始化对象
-(id)initWithCoder:(NSCoder *)aDecoder{

if (self = [super init]) {
    _num = [aDecoder decodeIntForKey:@"num"];
    _name = [[aDecoder decodeObjectForKey:@"name"] copy];
}
return self;
}