Xcode error missing file

Code builds but the app does not run. Exact ?

When do you get this message ?

Did you try to do an oprion-clean build folder ?

COde builds and the app runs. I'm not sure when I started to get this message. What is an oprion-clean build folder?

When you open project in XCode, you have, in Project Menu a Clean Build Folder.

That forces to recreate the build command.

option clean mean you hold option key down when calling this menu command. That forces a deeper clean (somehow).

That's a good practice when something weird occurs in XCode. It is harmless and can solve many issues (like impossible connection between IB and code, or apparently missing file, …).

But if it compiles and run, It would probably don't change anything here.

What is the consequence of the message : does app crash ?

Could you find when precisely you get the message ? From which point in code ?

May be you could add breakpoints or print statement to isolate where the error is.