Question

I’m trying to save some time / make my code readable. I have a lot of ‘isXXX’ messages that return BOOL. I am constantly adding more ‘is’ messages. Is it possible to make a macro that’s expandable at pre-compile time via a list.

I want to specify:
isMacro(1, 2, 3).

And for each of those, I want the macro to expand it into a full -(BOOL)is1 {…}, -(BOOL)is2…

It seems like this would be a good use of the precompiler macro expansion, but I’m not sure how to implement the isMacro(…) part. (Specifically, the … that expands into full functions before compile).

— Update:

The ‘is’ methods are all dynamically computed, but they are all common.

I’m testing a single variable against an enum value and determining whether it’s equal. I can’t @synthesize them, because it’s dynamic. I have all of them in a @property for convenience. I just want something that’s like @synthesize, where I can list all of them, and create a dynamic response for each isXXX method.

Also, I don’t want to run isCheck:(opMode)mode, since there is no pre-compile checking to make sure it’s a valid enum value.

All of the is functions are in the following format:
-(BOOL) isTurtle { return operationMode == Turtle; } The key is that I want it to function as a property for simplicity. Therefore, I don’t want something like is:(opMode)mode, where I have to specify BOOL res = [obj is:Tutle];

Answer 1

If you could use Boost.Preprocessor, the BOOST_PP_REPEAT_FROM_TO macro should suit your need.

#include <boost/preprocessor/repetition/repeat_from_to.hpp>

#define IS_METHODS(depth, n, aux) -(BOOL)is ## n { return aux == n; } 

@implementation Foo
BOOST_PP_REPEAT_FROM_TO(1, 31, IS_METHODS, operationMode)
@end

If you can’t, you’re out of luck. Implementing BOOST_PP_REPEAT_FROM_TO is about the same effort as just writing the 30+ functions directly.

Also I don’t see how [obj isMode:12] is really worse than obj.is12. The former also allows a variable mode, and is less cryptic to other programmers (think about the maintenance effort).