OC文件存储-补充

NSKeyedArchiver-对象归档

对象归档是指将对象写入文件保存在硬盘上，再次打开程序可以还原对象。（序列化、持久化）

归档形式

• 对foundation库中的对象进行归档

• 单一对象

• 归档

• NSArray * arr = @[@1, @"sda"];
  NSString *homePath = NSHomeDirectory();
  NSString *path = [homePath stringByAppendingPathComponent:@"test.j"];// admin/目录下
  扩展名随便取都行
  
  bool res = [NSKeyedArchiver archiveRootObject:arr toFile:path];
  if(res){
      NSLog(@"succes");
  }

• 解归档

• NSString *home = NSHomeDirectory();
  NSString *path = [home stringByAppendingPathComponent:@"test.j"];
  NSArray * array = [NSKeyedUnarchiver unarchiveObjectWithFile:path];
  NSLog(@"%@", array);

• 缺点：一个归档对应一个解归档，类型多之后不好分辨类型

• 多个对象

• 归档

• 使用NSData实例作为归档的数据存储
• 添加归档的内容（key-value）
• 完成归档
• 将归档数据存入磁盘

• NSString *home = NSHomeDirectory();
  NSString *path = [home stringByAppendingPathComponent:@"test.j"];
  
  NSMutableData *data = [NSMutableData data];
  NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];
  
  NSArray *array = @[@123, @"abc"];
  [archiver encodeObject:array forKey:@"nsarray"];
  [archiver encodeInt:2 forKey:@"count"];
  [archiver finishEncoding];
  
  BOOL res = [data writeToFile:path atomically:NO];
  if(res){
      NSLog(@"succes");
  }

• 解归档

• 从磁盘读取文件，生成NSData实例
• 根据Data实例创建和初始化解归档实例
• 解归档，根据key访问value

• NSString *home = NSHomeDirectory();
      NSString *path = [home stringByAppendingPathComponent:@"test2.j"];
  
      NSData *data = [NSData dataWithContentsOfFile:path];
      NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
      这是老的初始化方式，新的要将安全编码设为NO
  //    NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingFromData:data error:nil];
  //    [unarchiver     setRequiresSecureCoding:NO];
      int count = [unarchiver decodeIntForKey:@"count"];
      NSArray *array = [unarchiver decodeObjectForKey:@"nsarray"];
      [unarchiver finishDecoding];
      NSLog(@"count = %d, array = %@", count, array);

• 自定义对象进行归档（需要实现归档协议，NSCodeing[类似于java中的serilaizable)

• 实例

• // 遵守 NSCoding 协议
  @interface Dog : NSObject <NSCoding>
  
  @property (nonatomic, assign)int age;
  @property (nonatomic, copy)NSString *name;
  
  + (Dog *)dogWithName:(NSString *)name andAge:(int)age;
  
  @end

• // 实现 NSCoding 协议方法
  @implementation Dog
  
  // 归档 方法，使用编码器将对象编码成二进制数据流，归档（持久化存储）
  - (void)encodeWithCoder:(NSCoder *)aCoder{
  
          [aCoder encodeInt:self.age forKey:@"age"];
          [aCoder encodeObject:self.name forKey:@"name"];
  }
  
  // 反归档 方法，将保存在磁盘上的二进制数据流，解码成 OC 对象
  - (id)initWithCoder:(NSCoder *)aDecoder{
      if(self = [super init]){
          self.age = [aDecoder decodeIntForKey:@"age"];
          self.name = [aDecoder decodeObjectForKey:@"name"];
      }
          return self;
  }
  
  @end

• #import "Dog.h"
  
  // 文件路径
  NSString *achiverPath = [NSHomeDirectory() stringByAppendingString:@"/Desktop/dogAchiverFile"];
  
  Dog *dog = [Dog dogWithName:@"xiao hei" andAge:5];
  
  // 归档
  
  // 归档到文件
  BOOL bl = [NSKeyedArchiver archiveRootObject:dog toFile:achiverPath];
  
  // 反归档
  
  // 从文件反归档
  Dog *dogFromAchiverFile = [NSKeyedUnarchiver unarchiveObjectWithFile:achiverPath];

归档后的文件是加密的，属性列表是明文（参考OC中常用的类、数据类型、数据结构及结构体）