iOS FileSize 转成string

    NSString *fileURLString = [self.docInteractionController.URL path];

    NSDictionary *fileAttributes = [[NSFileManager defaultManager] attributesOfItemAtPath:fileURLString error:nil];

    NSInteger fileSize = [[fileAttributes objectForKey:NSFileSize] intValue];

    NSString *fileSizeStr = [NSByteCountFormatter stringFromByteCount:fileSize

                                                           countStyle:NSByteCountFormatterCountStyleFile];