/**

• 计算单个文件大小
  */
  +(long long)fileSizeAtPath:(NSString *)filePath{

  NSFileManager *manager = [NSFileManager defaultManager];

  if ([manager fileExistsAtPath :filePath]){

  return [[manager attributesOfItemAtPath :filePath error : nil ] fileSize];
  

  }
  return 0 ;

}

作者：iOS_凯
链接：http://www.jianshu.com/p/5ebe4f21c486
來源：简书
著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。
/**

• 清理缓存
  */
  +(void)cleanCache:(cleanCacheBlock)block
  {
  dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
  //文件路径
  NSString *directoryPath=[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) firstObject];

  NSArray *subpaths = [[NSFileManager defaultManager] contentsOfDirectoryAtPath:directoryPath error:nil];
  
  for (NSString *subPath in subpaths) {
      NSString *filePath = [directoryPath stringByAppendingPathComponent:subPath];
      [[NSFileManager defaultManager] removeItemAtPath:filePath error:nil];
  }
  //返回主线程
  dispatch_async(dispatch_get_main_queue(), ^{
      block();
  });
  

  });

}