XCode Debug Flag for Swift Posted on 2016-04-16 | In CocoaSet Debug Flag in XCode for SwiftOpen ‘Build Settings’ for Project (not target)Search ‘Swift Compiler - Custom Flags‘. Add a -D DEBUG entry in Other Swift FlagsUse Debug Flag in Swift12345#if DEBUG print("I'm running in DEBUG mode")#else print("I'm running in a non-DEBUG mode")#endif