iOS数据持久化存储-NSKeyedArchiver

归档文件

归档(称为序列化)是把对象转为字节码，以文件的形式存储到磁盘上；程序运行过程中或者当再次重写打开程序的时候，可以通过解归档（反序列化）还原这些对象。归档和解归档用于少量数据的持久化存储和读取。

归档和解归档常用API

//NSKeyedArchiver  API
+ (BOOL)archiveRootObject:(id)rootObject toFile:(NSString *)path;

- (instancetype)initForWritingWithMutableData:(NSMutableData *)data;

- (void)finishEncoding;

- (void)encodeObject:(nullable id)objv forKey:(NSString *)key;
- (void)encodeBool:(BOOL)boolv forKey:(NSString *)key;
- (void)encodeInt:(int)intv forKey:(NSString *)key;
- (void)encodeFloat:(float)realv forKey:(NSString *)key;
- (void)encodeDouble:(double)realv forKey:(NSString *)key;

//NSKeyedUnarchiver   API
+ (nullable id)unarchiveObjectWithData:(NSData *)data;
+ (nullable id)unarchiveObjectWithFile:(NSString *)path;

- (instancetype)initForReadingWithData:(NSData *)data;

- (void)finishDecoding;

- (nullable id)decodeObjectForKey:(NSString *)key;
- (BOOL)decodeBoolForKey:(NSString *)key;
- (int)decodeIntForKey:(NSString *)key;
- (float)decodeFloatForKey:(NSString *)key;
- (double)decodeDoubleForKey:(NSString *)key;

归档的方式：

• 针对对象进行归档（NSArray，NSDictionary等）
• 对自定义的内容进行归档
• 对自定义的对象进行归档

1、针对对象进行归档

- (void)objArchiver {
    
    //归档（序列化）
    NSArray *archiverAry = @[
                             @{@"Eugene" : @"ZhangYanJin"},
                             @{@"Chana" : @"LiChang"}
                             ];
    NSString *filePath = [self filePathWithName:@"Object"];
    if ([NSKeyedArchiver archiveRootObject:archiverAry toFile:filePath]) {
        NSLog(@"\n\n\n归档成功：路径%@",filePath);
    }
    
    //解归档 (反序列化)
    NSArray *unArchiverAry = [NSKeyedUnarchiver unarchiveObjectWithFile:filePath];
    NSLog(@"\n解归档成功 %@",unArchiverAry);
    
    /**
     总结：
     *优点：归档和解归档操作步骤简单方便
     *缺点：一次只能归档一个对象，如果归档多个对象，需要分开麻烦，操作繁琐费时
     */
}

- (void)customContentArchiver {
    
    //归档
    //1、使用Data存放归档数据
    NSMutableData *archiverData = [NSMutableData data];
    
    //2、根据Data实例创建和初始化归档对象
    NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:archiverData];
    
    //3、添加归档内容（设置键值对）
    [archiver encodeObject:@"Eugene" forKey:@"name"];
    [archiver encodeObject:@"man" forKey:@"sex"];
    [archiver encodeInt:25 forKey:@"age"];
    [archiver encodeObject:@[@"OC",@"Swift",@"Html"] forKey:@"laguage"];
    [archiver encodeObject:@{@"favorite" : @"cook"} forKey:@"life"];
    [archiver encodeCGPoint:CGPointMake(1.0, 2.0) forKey:@"point"];
    
    //4、完成归档
    [archiver finishEncoding];
    
    //5、将归档的信息存储到磁盘上
    NSString *filePath = [self filePathWithName:@"CustomContent"];
    if ([archiverData writeToFile:filePath atomically:YES]) {
        NSLog(@"\n\n\n归档成功：路径%@",filePath);
    }
    
    //解归档
    //1、从磁盘读取文件，生成NSData实例
    NSData *unarchiverData = [NSData dataWithContentsOfFile:filePath];

    //2、根据Data实例创建和初始化解归档对象
    NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:unarchiverData];

    //3、解归档，根据key值访问
    NSString *name = [unarchiver decodeObjectForKey:@"name"];
    NSDictionary *life = [unarchiver decodeObjectForKey:@"life"];
    NSLog(@"\n解归档成功: %@ %@",name,life);
    
    //4、完成解归档
    [unarchiver finishDecoding];

    /**
     总结：
     *优点：可以同时归档多个对象、以及不同类型的对象（如：Int、CGFloat、CGPoint）
     *缺点：这里的对象都是基本类型数据，如果我想对自己定义类生成的实例对象进行归档，这样做将使操作又变得繁琐费时了
     */
}

- (void)customObjectArchiver {
    
    //序列化和反序列化遵循NSCoding协议的自定义类
    
    //归档
    Person *person = [[Person alloc] init];
    person.name = @"Eugene";
    person.sex = @"man";
    person.age = 25;
    person.height = 175;
    
    NSString *filePath = [self filePathWithName:@"CustomObject"];

    if ([NSKeyedArchiver archiveRootObject:person toFile:filePath]) {
        NSLog(@"\n\n\n归档成功：路径%@",filePath);
    }
    
    //解归档
    Person *unArchiverObj = [NSKeyedUnarchiver unarchiveObjectWithFile:filePath];
    NSLog(@"\n解归档成功: %@ %@",unArchiverObj,unArchiverObj.name);
    
}

- (NSString *)filePathWithName:(NSString *)name {

    name = [[NSString alloc] initWithFormat:@"%@.archiver",name];
    
    //归档后的文件是加密的，所以归档文件的扩展名可以随意取,我这里后缀用archiver
    return [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:name];
}

注意：

• 1、默认情况下，只能对NSDate, NSNumber, NSString, NSArray, or NSDictionary来进行归档。
• 2、若对自定义的对象进行归档，需要实现NSCoding协议，并实现NSCoding方法。
• NSCoding协议的方法：
• - (void)encodeWithCoder:(NSCoder *)aCoder;
• - (instancetype)initWithCoder:(NSCoder *)aDecoder;
• 3、如果用了继承，则子类一定要重写NSCoding协议的两个方法。

附：归档Demo

写在最后

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