数据存储之Archiver、Unarchiver、偏好设置

• 数组的归档
• 对象的归档
• NSData多个对象的归档
• NSArray多个对象的归档
• 偏好设置的存储

1.NSString、NSDictionary、NSArray、NSData、NSNumber等类型的对象，可以直接用NSKeyedArchiver进行归档和恢复

2.不是所有的对象都可以直接用这种方法进行归档，只有遵守了NSCoding协议的对象才可以

1⃣️归档和恢复

支持复杂的数据对象，包括自定义对象。

对自定义对象进行归档处理，需要实现NSCoding协议

2⃣️NSCoding协议方法

encodeWithCoder

initWithCoder

3⃣️NSKeyedArchiver & NSKeyedUnarchiver

4⃣️对于多个对象可以通过NSArray或者NSData进行归档

一、数组的归档

// 演练1 NSArray归档
// 注意，可以通过修改文件名查看归档文件内容
NSString *path = [docDir stringByAppendingPathComponent:@"array.archive"];
// 定义数组
NSArray *array = @[@"张三", @"李四", @"王五"];
// 归档数组
[NSKeyedArchiver archiveRootObject:array toFile:path];

// 恢复数组
NSArray *unarchivedArray = [NSKeyedUnarchiver unarchiveObjectWithFile:path];
NSLog(@"%@", unarchivedArray);

二、对象的归档

1⃣️重写NSCoding两个方法

// 归档
- (void)encodeWithCoder:(NSCoder *)aCoder
{
    [aCoder encodeObject:_name forKey:@"name"];
    // 图像数据
    NSData *imageData = UIImagePNGRepresentation(_userImage);
    [aCoder encodeObject:imageData forKey:@"imageData"];
    [aCoder encodeInt:_age forKey:@"age"];
    [aCoder encodeObject:_phone forKey:@"phone"];
}

// 恢复
- (id)initWithCoder:(NSCoder *)aDecoder
{
    [self setName:[aDecoder decodeObjectForKey:@"name"]];
    // 图像数据
    NSData *imageData = [aDecoder decodeObjectForKey:@"imageData"];
    [self setUserImage:[UIImage imageWithData:imageData]];
    [self setAge:[aDecoder decodeIntForKey:@"age"]];
    [self setPhone:[aDecoder decodeObjectForKey:@"phone"]];
    
    return self;
}

2⃣️归档和恢复

// 归档文件路径
NSArray *documents = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *path = [documents[0]stringByAppendingPathComponent:@"personInfo.plist"];

// 新建Person对象
Person *person = [Person initPersonWithName:_userNameText.text image:_userImageView.image age:_ageText.text.intValue phone:_phoneText.text];

// 归档用户数据
[NSKeyedArchiver archiveRootObject:person toFile:path];

// 恢复文件路径
NSArray *documents = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *path = [documents[0]stringByAppendingPathComponent:@"personInfo.plist"];

// 恢复Person对象
Person *person = [NSKeyedUnarchiver unarchiveObjectWithFile:path];

[_userNameText setText:person.name];
[_userImageView setImage:person.userImage];
[_ageText setText:[NSString stringWithFormat:@"%d", person.age]];
[_phoneText setText:person.phone];

三、NSData多个对象的归档（用于不同对象）

1⃣️归档

// 演练3. 归档多个对象
- (void)archivedMultiObjects
{
    // 获取文档目录
    NSArray *documents = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    // 存档路径
    NSString *path = [documents[0]stringByAppendingPathComponent:@"multiUsers.plist"];

    Person *person1 = [Person initPersonWithName:@"张三" image:[UIImage imageNamed:@"头像1.png"] age:18 phone:@"110"];
    Person *person2 = [Person initPersonWithName:@"李四" image:[UIImage imageNamed:@"头像2.png"] age:32 phone:@"120"];

    // 新建一块可变的数据区
    NSMutableData *data = [NSMutableData data];
    // 将数据区连接到一个NSKeyedArchiver对象
    NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc]initForWritingWithMutableData:data];
    // 开始存档对象，存档的数据都会存储到NSMutableData中
    [archiver encodeObject:person1 forKey:@"person1"];
    [archiver encodeObject:person2 forKey:@"person2"];
    // 存档完毕(一定要调用这个方法)
    [archiver finishEncoding];
    // 将存档的数据写入文件
    [data writeToFile:path atomically:YES];
}

2⃣️恢复

- (void)unarchiverPersonInfo:(UIButton *)sender
{
    // 演练3. 恢复NSData归档的多个数据
    // 获取文档目录
    NSArray *documents = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    // 存档路径
    NSString *path = [documents[0]stringByAppendingPathComponent:@"multiUsers.plist"];
    
    // 演练4. 使用NSArray归档多个对象
    NSString *path2 = [documents[0]stringByAppendingPathComponent:@"multiUsers2.plist"];
    NSArray *array = [NSKeyedUnarchiver unarchiveObjectWithFile:path2];
    for (Author *author in array) {
        NSLog(@"%@ %d %@ %@", author.name, author.age, author.phone, author.bookName);
    }

    // 从文件读取数据
    NSData *data = [NSData dataWithContentsOfFile:path];
    // 根据数据，解析成一个NSKeyedUnarchiver对象
    NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc]initForReadingWithData:data];
    // 恢复对象
    Person *person1 = [unarchiver decodeObjectForKey:@"person1"];
    Person *person2 = [unarchiver decodeObjectForKey:@"person2"];
    // 恢复完毕(一定要调用这个方法)
    [unarchiver finishDecoding];

    // 根据按钮Tag设置UI
    if (sender.tag == 0) {
        [_userNameText setText:person1.name];
        [_userImageView setImage:person1.userImage];
        [_ageText setText:[NSString stringWithFormat:@"%d", person1.age]];
        [_phoneText setText:person1.phone];
    } else {
        [_userNameText setText:person2.name];
        [_userImageView setImage:person2.userImage];
        [_ageText setText:[NSString stringWithFormat:@"%d", person2.age]];
        [_phoneText setText:person2.phone];
    }
}

 四、NSArray多个对象的归档（用于相同对象）

1⃣️写一个Author类，继承Person

类中需要重写两个方法

// 归档
- (void)encodeWithCoder:(NSCoder *)aCoder
{
    [super encodeWithCoder:aCoder];
    
    [aCoder encodeObject:_bookName forKey:@"bookName"];
}

// 恢复
- (id)initWithCoder:(NSCoder *)aDecoder
{
    self = [super initWithCoder:aDecoder];
    
    if (self) {
        _bookName = [aDecoder decodeObjectForKey:@"bookName"];
    }
    
    return self;
}

2⃣️使用NSArray归档

// 演练4. 使用NSArray归档多个对象
- (void)archivedMultiObjectsWithArray;
{
    // 获取文档目录
    NSArray *documents = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    // 存档路径
    NSString *path = [documents[0]stringByAppendingPathComponent:@"multiUsers2.plist"];

    Author *author1 = [Author initPersonWithName:@"张大师" image:[UIImage imageNamed:@"头像1.png"] age:30 phone:@"110" bookName:@"C语言基础"];
    Author *author2 = [Author initPersonWithName:@"张大师" image:[UIImage imageNamed:@"头像1.png"] age:30 phone:@"110" bookName:@"C++宝典"];

    NSArray *array = @[author1, author2];

    // 注意此处不能使用 [array writeToFile:path atomically:YES];
    [NSKeyedArchiver archiveRootObject:array toFile:path];
}

3⃣️解档

NSArray *documents = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    // 存档路径
    NSString *path = [documents[0]stringByAppendingPathComponent:@"multiUsers.plist"];
    
    // 演练4. 使用NSArray归档多个对象
    NSString *path2 = [documents[0]stringByAppendingPathComponent:@"multiUsers2.plist"];
    NSArray *array = [NSKeyedUnarchiver unarchiveObjectWithFile:path2];
    for (Author *author in array) {
        NSLog(@"%@ %d %@ %@", author.name, author.age, author.phone, author.bookName);
    }

五、偏好设置的存储

注意：UserDefaults设置数据时，不是立即写入，而是根据时间戳定时地把缓存中的数据写入本地磁盘。所以调用了set方法之后数据有可能还没有写入磁盘，应用程序就终止了。

出现以上问题，可以通过调用synchornize方法强制写入：

[defaults synchronize];

1⃣️偏好设置保存

    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    
    [defaults setObject:@"王二麻子" forKey:@"UserName"];
    [defaults setFloat:18.5 forKey:@"fontSize"];
    [defaults setBool:NO forKey:@"purchased"];
    
    [[NSUserDefaults standardUserDefaults]setObject:@"110" forKey:@"Phone"];
    // 同步命令
    [[NSUserDefaults standardUserDefaults]synchronize];

2⃣️取出

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSString *userName = [defaults objectForKey:@"userName"];
float fontSize = [defaults floatForKey:@"fontSize"];
BOOL autoLogin = [defaults boolForKey:@"autoLogin"];