小白的逆袭

错误提示：   "_OBJC_CLASS_$_ClassName", referenced from:  objc-class-ref in main.o ld: symbol(s) not found for architecture x86_64 clang: error: linker command failed with exit code 1 (use -v to se

int num; scanf("%d",&num);   switch(num){ default:  默认语句 break; case 1:  语句一 break; case 2: 语句 二 break; case 3: 语句三 case 4:  语句四 case 5:  语句五 break; }