Question

Is it generally valid that a macro is used to create a method name? I mean…actually it’s just simple text replacement before the compiler actually runs, right?

Answer 1

Yes, it is valid; macro expansion occurs before the compiler even reads the code. The main limitation is that one cannot embed a preprocessor directive within a preprocessor directive. So, for example:

// This is ok:
#define PREFIX(X) this_name_is_prefixed_ ## X
// ...
- (void) PREFIX(doSomething):id;
// ...

// But this isn't:
#define IMPORT(X) #import X
IMPORT(<Foundation/Foundation.h>) // <= Don't expect this to work

With the exception of the “#import” directive, Objective-C’s preprocessor is basically the same as the C preprocessor. (The “#import” is like “#include”, except that #import implies include only once, so preprocessor guards are not required for headers that are included only with #import).