1.介紹

一種可以把任意對象直接保存到文件的方式琅坡。
歸檔：把對象保存到文件中雄坪。
解檔：從文件中讀取對象孵户。

2.注意：

歸檔會先清空文件嘁圈，然后重新寫入逗扒。

3.歸檔對象的寫法

1.對象要實現 NSCoding 協議

@interface Student : NSObject<NSCoding>

@property(nonatomic,copy)NSString *name;

@property(nonatomic,assign) CGFloat score;

@property(nonatomic,assign) BOOL sex;

@end

//1.基類寫法
/**
 *  告訴系統需要歸檔的屬性
 *
 *  @param aCoder 解析器
 */
- (void)encodeWithCoder:(NSCoder *)aCoder{
    [aCoder encodeObject:self.name forKey:@"name"];
    [aCoder encodeFloat:self.score forKey:@"score"];
    [aCoder encodeBool:self.sex forKey:@"sex"];
}

/**
 *  告訴系統解檔出來的數據都需要怎么賦值
 *
 *  @param aDecoder 解析器
 *
 *  @return 對象
 */
- (instancetype)initWithCoder:(NSCoder *)aDecoder{
    if (self = [super init]) {
        self.name = [aDecoder decodeObjectForKey:@"name"];
        self.score = [aDecoder decodeFloatForKey:@"score"];
        self.sex = [aDecoder decodeBoolForKey:@"sex"];
    }
    return self;
}


//1.子類寫法
- (void)encodeWithCoder:(NSCoder *)aCoder{
    //一定要調用一下父類的方法
    [super encodeWithCoder: aCoder];
    [aCoder encodeObject:self.name forKey:@"name"];
    [aCoder encodeFloat:self.score forKey:@"score"];
    [aCoder encodeBool:self.sex forKey:@"sex"];
}

- (instancetype)initWithCoder:(NSCoder *)aDecoder{
    //一定要調用一下父類的方法
    if (self = [super initWithCoder: aDecoder]) {
        self.name = [aDecoder decodeObjectForKey:@"name"];
        self.score = [aDecoder decodeFloatForKey:@"score"];
        self.sex = [aDecoder decodeBoolForKey:@"sex"];
    }
    return self;
}

4.歸檔 -- NSKeyedArchiver

//歸檔一個對象
- (void)save{
    //1.準備對象
    Student *stu = [[Student alloc] init];
    stu.name = @"zhangsan";
    stu.score = 90;
    stu.sex = YES;
    //2.要存儲的文件路徑
    NSString *filePath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    filePath = [filePath stringByAppendingPathComponent:@"student.data"];
    //3.歸檔
    [NSKeyedArchiver archiveRootObject:stu toFile:filePath];
}

//歸檔一組對象
- (void)save{
    //1.準備對象
    Student *stu = [[Student alloc] initWithName:@"zhangsan" withScore:90 withSex:YES];
    
    Student *stu1 = [[Student alloc] initWithName:@"lisi" withScore:90 withSex:YES];
    
    NSArray *arr = @[stu,stu1];
    //2.要存儲的文件路徑
    NSString *filePath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    filePath = [filePath stringByAppendingPathComponent:@"student.data"];
    //3.歸檔
    [NSKeyedArchiver archiveRootObject:arr toFile:filePath];
}

5.解檔 -- NSKeyedUnarchiver

//解析單一對象
- (void)getData{
    //1.要存儲的文件路徑
    NSString *filePath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    filePath = [filePath stringByAppendingPathComponent:@"student.data"];
    //2.解檔
    Student *stu = [NSKeyedUnarchiver unarchiveObjectWithFile:filePath];
}

//解檔一組對象
- (void)getData{
    //2.要存儲的文件路徑
    NSString *filePath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
    filePath = [filePath stringByAppendingPathComponent:@"student.data"];
    //3.解檔
    NSArray *stus = [NSKeyedUnarchiver unarchiveObjectWithFile:filePath];
    NSLog(@"%@",stus);
}