IOS 文件读写操作的实现

- （void）writeFile：（NSString *）file
{
 //创建文件管理器
 NSFileManager *fileManager = [NSFileManager defaultManager];
 
 //获取路径
 //1、参数NSDocumentDirectory要获取的那种路径
 NSArray* paths = NSSearchPathForDirectoriesInDomains（NSDocumentDirectory，NSUserDomainMask，YES;
 //2、得到相应的Documents的路径
 NSString* DocumentDirectory = [paths objectAtIndex:0];
 //3、更改到待操作的目录下
 [fileManager changeCurrentDirectoryPath:[DocumentsDirectory stringByExpandingTildeInPath]];
 //4、创建文件fileName文件名称，contents文件的内容，如果开始没有内容可以设置为nil，attributes文件的属性，初始为nil
 [fileManager removeItemAtPath：@“username” error:nil];
 NSString *path = [documentsDirectory stringByAppendingPathComponent:@"username"];
 //5、创建数据缓冲区
 NSMutableData *writer = [[NSMutableData alloc] init];
 //6、将字符串添加到缓冲中
 [writer appendData:[file dataUsingEncoding:NSUTF8StringEncoding]];
 //7、将其他数据添加到缓冲中
 //将缓冲的数据写入到文件中
 [writer writeToFile:path atomically:YES];
 [writer release];
}

- (NSString *)readFile
{
 //创建文件管理器
 NSFileManager *fileManager = [NSFileManager defaultManager];
 //获取路径
 NSArray* paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask,YES);
 NSString *documentsDirectory = [paths objectAtIndex:0];
 
 [fileManager changeCurrentDirectoryPath:[documentsDirectory stringByExpandingTildeInPath]];
 
 //获取文件路劲
 NSString* path = [documentsDirectory stringByAppendingPathComponent:@"username"];
 NSData* reader = [NSData dataWithContentsOfFile:path];
 return [[NSString alloc] initWithData:reader encoding:NSUTF8StringEncoding];
      

}