Hello! Why they can not communicate with each other? Macro declared in another expanded macro is not visible for compiler and just ignored. Is it a bug or is a limit of macro system? Maybe it will be fixed in future?
rhysmorgan
(Rhys Morgan)
2
What do you mean by "communicate"?
Regardless, macros can only work on the syntax they're provided or are attached to.
I mean if one macro generates by another macro then inner macro will not be expanded
rhysmorgan
(Rhys Morgan)
4
It should do!
Xcode's "Expand macro" feature only expands macros by one level, I believe, because that's how the macro works. You should be able to expand the #Preview macro in that as well, and see what's happening.
sjavora
(Šimon Javora)
5
You can expand it manually, but the inner #Preview won't make Xcode display the preview pane. I too would like to know if this is intended or just not implemented, as I'm facing the exact same situation (with inner #Preview).
(why? See How to get access to a View defined inside a #Preview macro)
Pippin
(Ethan Pippin)
6
Xcode does weird things with to make SwiftUI previews possible, especially with #Preview. For example, it generates an arbitrarily named macro at the global scope without declaring any names on the macro declaration and the new structure is hidden from user code - Xcode takes any preview-code and handles it separately, but only if it's written in an expected place within the raw file/AST.
However that's all from my own investigation of trying to reverse engineer how previews work, and I could be wrong.
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