Question

I wonder if macros only have pros in any programming language. As there must be the limit we can create macros, and in frequency of use.

Suppose we create 100 macros in a class and imported that in 100 class of an application project. Is this a right approach?

Answer 1

#define is useful for:

• header include guards for C and C++ headers (idiom: #include C and C++ headers, #import ObjC headers)
• conditional compilation for language compatibility (e.g. UIKIT_EXTERN) which must be resolved during preprocessing.
• conditional compilation for platform/compiler/version specific declarations (e.g. NS_AVAILABLE_IOS()) which must be resolved during preprocessing.
• Assertion macros. Specifying the information such as the file, line and expression is just too noisy and error-prone.

for everything else, there is an alternative which will save you headaches along the way.

Suppose we create 100 macros in a class and imported that in 100 class of an application project. Is this a right approach?

no – that is terrifying 🙂

Cons

There are many. Too often, the program will be difficult to understand by humans and programs (compiler, parser, indexer) alike. It’s a good way to introduce bugs, and completely replace text of unrelated programs (via a simple #import). There are more modern replacements for pretty much everything (e.g. functions, inline, typedef, constants, enums) — Allow the compiler to make your life easier!