Foundation对象 <-> 文件

• NSArray

        NSArray *array = @[@1,@2,@3];
        [array writeToFile:kFileAddress
                atomically:YES];

• NSDictionary

        NSDictionary *dictionary = @{@"1" : @1 , @"2" : @2 , @"3" : @3};
        [dictionary writeToFile:kFileAddress
                     atomically:YES];

• NSString

        NSString *string = @"hello world";
        [string writeToFile:kFileAddress
                 atomically:YES // 是否先将内容写入临时文件,成功后再将临时文件目标文件交换
                   encoding:NSUTF8StringEncoding
                      error:&writeToFileError];
        if (writeToFileError) {
            NSLog(@"%@",[writeToFileError localizedDescription]);
            writeToFileError = nil;
        }

• NSData

        NSData *data = [[NSData alloc] init];
        [data writeToFile:kFileAddress
                  options:NSDataWritingAtomic // 先将内容写入临时文件,成功后再把临时文件和目标文件交换
                    error:&writeToFileError];
        if (writeToFileError) {
            NSLog(@"%@",[writeToFileError localizedDescription]);
            writeToFileError = nil;
        }

自定义对象 <-> NSData <->文件

• 自定义类遵循 NSCoding 协议,实现 encodeWithCoder:和 initWithCoder:方法

- (void)encodeWithCoder:(NSCoder *)aCoder {
    
    [aCoder encodeObject:self.name forKey:kKeyForName];
    [aCoder encodeObject:self.phoneNumber forKey:kKeyForPhoneNumber];
}

- (instancetype)initWithCoder:(NSCoder *)aDecoder {
    
    self = [super init];
    if (self) {
        self.name = [aDecoder decodeObjectForKey:kKeyForName];
        self.phoneNumber = [aDecoder decodeObjectForKey:kKeyForPhoneNumber];
    }
    
    return self;
}

• 用 NSCoder 子类 NSKeyedArchiver 和 NSKeyedUnarchiver

        // 将 ZWQPerson 对象写入文件
        ZWQPerson *personA = [[ZWQPerson alloc] initWithName:@"David" phoneNumber:@12345678912];
        
        NSError *writeToFileError = nil;
        
        NSData *dataOfZWQPersonA = [NSKeyedArchiver archivedDataWithRootObject:personA];
        [dataOfZWQPersonA writeToFile:kFileAddress
                             options:NSDataWritingAtomic
                               error:&writeToFileError];
        
        if (writeToFileError) {
            
            NSLog(@"%@",[writeToFileError localizedDescription]);
        }
        
        // 从文件中读取 ZWQPerson
        NSData *dataOfZWQPersonB = [NSData dataWithContentsOfFile:kFileAddress];
        ZWQPerson *personB = [NSKeyedUnarchiver unarchiveObjectWithData:dataOfZWQPersonB];
        
        NSLog(@"If personA is equal to personB?   %@", [personA isEqualToPerson:personB] ? @"YES" : @"NO" ); // 应该返回 YES