How to link headerfile and sourcefile by C++

edit

For source code to find header files, the CMakeLists.txt needs to be changed.

For example if your package formate is

dummy_pkg/
   src/
   include/
   CmakeLists.txt
   package.xml

Then in your CMakeLists.txt, you need to add

include_directories(
  include
)

will include header files in the include/ directory. If you are looking for headers in other ros packages then also add ${catkin_INCLUDE_DIRS} inside those brackets.