How do I use a relative path in Xcode project settings?

Question

How do I use a relative path in Xcode project settings?

Answer 1

Using Xcode 9:

It may be intended for Xcode to always use relative file paths based on the directory that contains the xcodeproj, but sometimes this does not seem to be true, and in my case this may have been due to the fact that the project (directory and all) was copied from an earlier version. I had to do:

Target(top left)->Edit Scheme->Use Custom Working Directory

and then specify to use the directory containing my project file.