取自 NSString参考，可以使用：

NSString *theFileName = [[string lastPathComponent] stringByDeletingPathExtension];

lastPathComponent 调用将返回 thefile.ext ， stringByDeletingPathExtension 将从末尾删除扩展名。

The lastPathComponent call will return thefile.ext, and the stringByDeletingPathExtension will remove the extension suffic from the end.