What is a Swift macro?

You probably heard the term “macro” before in the context of programming. That’s perhaps because programming languages such as C/C++ have macros as well.

A macro is a structure that lets us define a code pattern that is being replaced by the compiler with a specific set of instructions.

Let’s see a short C example:

#define SQUARE(x) ((x) * (x))
int num = 5;
int result = SQUARE(num);

In our preceding code, we declare a macro called SQUARE that receives one parameter named X, and our compiler replaces it with (x) *(x).

The initial question that comes to mind is this: why? Can’t we just define a function?

So, in this case, a simple function that calculates a number’s square can be helpful here.

But a macro’s primary goal is not to replace functions, as they are great for several reasons:

• Code reuse: Notice that code reuse is not “functionality reuse.” Code reuse is where we...