In C/C++/Objective C you can define a macro using compiler preprocessors. Moreover, you can include/exclude some parts of code using compiler preprocessors.
Use Active Compilation Conditions setting in Build settings / Swift compiler - Custom flags.
ALPHA
, BETA
etc.Then check it with compilation conditions like this:
#if ALPHA
//
#elseif BETA
//
#else
//
#endif
Tip: You can also use
#if !ALPHA
etc.