How do I access a preprocessor macro from code in Xcode using Swift?

Question

How do I access a preprocessor macro in Xcode from Swift code for a string I've defined? Other stackoverflow posts show how to create the macros, but do not show me how to access them in code sufficiently.

For example, I have defined a constant called HELLO_WORLD_STRING = "Hello World!" in Preprocessor Macros Not Used in Precompiled Headers in the build settings as in the image:

How would I print that constant in the debug window, just as an example?

I actually need to use the value of the app name to set the title of a navigation bar, but I would like to take this route in order to do that.

I have tried using #if ... #endif statements, but the constant was not recognized.

What language are you using? Swift eschews the use of macros. #ifdef work, but defines, not so much. — Hack Saw
– Hack Saw, Commented Dec 6, 2018 at 8:03
And I have to ask: what benefit do you think you'd get by retrieving this value from the build system, rather than setting it for your self in your application delegate, say? — Hack Saw
– Hack Saw, Commented Dec 6, 2018 at 8:05
As far as I can tell, it's not possible in Swift. You can get the full path of the executable with Bundle.main.executablePath. — Hack Saw
– Hack Saw, Commented Dec 6, 2018 at 8:06
Yeah, so Swift is valiantly trying to kill off the use of macros, as they can make code hard to reason about, being one more place one needs to look for constants. — Hack Saw
– Hack Saw, Commented Dec 6, 2018 at 8:15

Maciej Gad · Accepted Answer · 2018-12-06 08:27:31Z

4

If you want to use syntax like:

 #if DEBUG_API_CALL
    print("Start loading \(method) \(url)")
 #endif

You have to add DEBUG_API_CALL (or other your name) to Active Compilation Conditions in the build settings tab:

answered Dec 6, 2018 at 8:27

Maciej Gad

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