Today I had a lot of fun trying to get Xcode to correctly use my swift compilation flags so that I can properly differentiate between develop, staging and production environments.

#if DEVELOP
        static let server_host = "..."
#elseif STAGING
        static let server_host = "..."
#elseif PRODUCTION
        static let server_host = "..."
#else
#error("You have not defined an environment for app credentials")
#endif

Here are the steps that do work

1. Add the appropriate build configurations to your app:
   • click on the app in the file list view
   • select the Project
   • under Info, use + to add new configurations. I am using:
   • Debug
   • Debug-Staging
   • Staging
   • Release
2. Now in Targets select your app again, find “Swift Compiler - Custom Flags”
   • for Debug builds, just adding it to the main line seems to work

   • for all other configurations, don’t add it to the main line (it does not seem to get picked up here), but instead, click the (+) and add it to “Any Architecture

     Any SDK”

   • Note: you don’t need -DFLAG as identified in some posts

Gotcha: this looks like it would work, but it does not (at this time)