iPhone Tutorials - "Duplicate Symbol _OBJ_IVAR_"

I am working on a personal review about XCode 4. Please, be patient!

XCode 4 gives me many troubles. The last one was a linker error

Duplicate Symbol _OBJ_IVAR_ a class

What happens?

• Maybe you declare #import "Classname.m" (with a .m instead than .h)
• XCode lists "Classname.h" and "Classname.m" two times. You have to "remove reference" for a copy from XCode.
  

It seems XCode4 gives many problems to iOS developers. I'll talk better in another post.