I’ve often wondered how to use those efficiently, and I’ve just found out how to do it. As always, they’re not difficult to implement – but not documented in a way that simple folk like me can understand it. Be that as it may…
Preprocessor Macros can be useful if you’d like to compile two different versions of the same Xcode Project, such as a Lite and a Pro version, or a separate iPhone and an iPad version. Rather than create separate Xcode Projects for each version, you have one project with two targets. Each target can build a different version from your code, making maintenance much simpler than having to change the same code in two projects.
How do they work?
Preprocessor Macros are directives executed by the compiler, so they’re not part of Objective C. We’ve used them many times before with the #import statement. But to stay with our Lite and Pro example: you can use a Preprocessor if/then statement to check which version is being compiled. For this, let’s define a Macro for the Pro version. Here’s how in Xcode 4.6:This content is for members only.
And that’s all there’s to it! This makes most sense with Targets which we’ll discuss next.