How to fix “SWIFT_VERSION '3.0' is unsupported, supported versions are: 4.0, 4.2, 5.0” error in Xcode 10.2?

Question

I\'m trying to run downloaded from app, try to open in Xcode and have an error:

\" Showing Recent Messages
:-1: SWIFT_VERSION \'3.0\' is unsu

Answer 1

I followed the instructions on this page and the error didn't resolve. Finally, went into

$ vim MyProject.xcodeproj/project.pbxproj

and found two instances where

SWIFT_VERSION = 3.0;

was still being referenced. I changed those to 5.0 and the error was gone. Not sure why those two were still there.