Swift写/保存/移动文件到iCloud驱动器。

I've been trying for over two days to write a file to iCloud drive. I have tried writing a simple text file directly, locally then moving it, using UIDocumentMenuViewController, etc. I'm not getting any errors with my code and stepping through debugger, it looks successful, but when I check to see if the file exists or at least the iCloud directory, there is nothing there. I tried on both the simulator and my iPhone, triggering iCloud synching, and everything else I can think of.I've been trying for over two days to write a f