计算单个文件的大小

- (long long) fileSizeAtPath:(NSString*) filePath{

  NSFileManager* manager = [NSFileManager defaultManager];

  if ([manager fileExistsAtPath:filePath]){
    
    return [[manager attributesOfItemAtPath:filePath error:nil] fileSize];
  }
  return 0;
}

计算文件夹的大小

- (float ) folderSizeAtPath:(NSString*) folderPath{

  NSFileManager* manager = [NSFileManager defaultManager];

  if (![manager fileExistsAtPath:folderPath]) return 0;

  NSEnumerator *childFilesEnumerator = [[manager subpathsAtPath:folderPath] objectEnumerator];

  NSString* fileName;

  long long folderSize = 0;

  while ((fileName = [childFilesEnumerator nextObject]) != nil){
    
      NSString* fileAbsolutePath = [folderPath stringByAppendingPathComponent:fileName];
    
      folderSize += [self fileSizeAtPath:fileAbsolutePath];
    
  }

  return folderSize/(1024.0*1024.0);

}