I have an iOS refactoring library that I want to work with and without the ARC compilation option. Is there a way to detect during compilation, like with an #ifdef, if ARC is available?
Yes, you can use the following:
#if __has_feature(objc_arc)
...
#endif
Even if you're using the latest version of LLVM, this will only evaluate to true if you're compiling with the -fobjc-arc option.
来源：https://stackoverflow.com/questions/7708267/check-for-arc-in-precompile