You can see: in the first image, the default project have DEBUG macro. So in perview, release code segment is grey. But!!! In edit scheme, I change all of item to release mode! (See second image) At this point, the DEBUG code block is still highlighted. If I compile and run it, the output is actually from the Release code block. In other words, I have changed all the modes in the scheme, but the preview mode is still in DEBUG.

I can't find any useful help about the content described in the title on Apple's official website. The relevant help on its official website is almost all based on OC language, and even their sample programs are written in OC language. Can I ask if SWIFT can only use the COM port through the bridge of OC-SWIFT?