Invalid token at start of a preprocessor expression Xcode [duplicate]

Question

This question already has an answer here:

Macro in Objective-C calling isEqualToString: produces error about invalid token (1 answer)

Closed 3 years ago.

#define A7VERSION() ({[[[[[UIDevice currentDevice] systemVersion] componentsSeparatedByString:@"."] objectAtIndex:0] intValue];})

#define IS_OS_7 A7VERSION()>=7

The above declaration seems to compile well.

But as soon as I add it a .m file I get the following exception "invalid token at start of a preprocessor expression". I am not able to understand where I could be wrong

@implementation AppViewController
#if IS_OS_7
….
#else
….  
#endif
@end

Answer 1

The problem has nothing to do with iOS 7.

Your #define does not lead to something that can be resolved at compile time. An #ifdef only works if the conditional is something that can be determined at compile time. It cannot be used to change behavior at runtime based on the environment an app is running on.