How to require ARC in a class?

问题:

I have an app with both ARC code and non-ARC code. The compiler will catch when I try to compile non-ARC code as ARC. How do I cause a compile time error/notice when my ARC code is erroneously compiled without ARC? Obviously, the code will compile. It will just leak. The static analyzer will catch the problem. I would rather find a way to leave a pragma or define in my ARC code.

The following is defined by Apple in objc-api.h:

/* OBJC_ARC_UNAVAILABLE: unavailable with -fobjc-arc */
#if !defined(OBJC_ARC_UNAVAILABLE)
#   if __has_feature(objc_arr)
#       define OBJC_ARC_UNAVAILABLE __attribute__((unavailable("not available in automatic reference counting mode")))
#   else
#       define OBJC_ARC_UNAVAILABLE
#   endif
#endif

My C-macro-fu is weak. How would I use it? Or, perhaps there is a better symbol to check?

P.S. I ask because I build much of my app from reusable libraries. I want to ensure that each file is compiled in the right way.

回答1:

The following should work:

#if !__has_feature(objc_arc)
#  error Compile me with ARC, please!
#endif

Place it at the top of your file.

回答2:

If it is a complete file, I would recommend adding -fno-objc-arc to the compiler flags to use the non-arc compiler.

Use the macro to compile "parts" of code with the non-arc compiler. for example, use this if you are writing a framework that will be used in both arc and non-arc code bases and write release, deallocs within this macro block