When I include "HelloWorld.h" into TestViewController.h it prompt error: 'iostream' file not found….
Is there any Objective-C files which imports TestViewController.h? At the stage of preprocessing header file becomes a part(along with the source file) of a translation unit, and if you're asking to include such header (with c++ libraries inclusion and c++ class definition) to Objective-C source file - then no, it's impossible. If you searching a way to compile and link .cpp and .m source files to one binary, you could make .mm wrapper unit to wire them together.