c++ : one file class-in-node to three files class, node, and header

edit

[Note: Prior to this question, my code and package compiled and functioned properly, the issue came from rearranging my file structure etc.]

I am trying to make a single node reusable by separating it into multiple files. This is probably more of a c++ question, but I'm not sure if i need to do something different in my code, or in my CMakeLists...

My original file had this structure:

#include <head_loc/manythings.h>
class ClassName
{
private:
    Multiple ClassVariables;
public:
  ClassName()    // Constructor for publishers etc..
    {    }
  output function1()     // do 1st thing
    {    }
  output functionN()     // do Nth thing
    {    }
};
int main(int argc, char** argv)
{
    ros::init(argc, argv, "ClassName_Node");
    ClassName CN;
    ros::spin();
    return 0;
}

My three new files have this structure: Node file:

#include <classheader.h>
int main(int argc, char** argv)
{
  ros::init(argc, argv, "ClassName_Node");
  ClassName CN;
  ros::spin();
  return 0;
}

Header file :

#ifndef _CLASSHEADER_H
#define _CLASSHEADER_H
#include <head_loc/manythings.h>
class ClassName
{
private:
  Multiple ClassVariables;
public:
  ClassName();    // Constructor for publishers etc..
  output function1();     // do 1st thing
  output functionN();     // do Nth thing
};
#endif

Class fucntions :

#include <classheader.h>
ClassName::ClassName()    // Constructor for publishers etc..
{    }
output ClassName::function1()     // do 1st thing
{    }
output ClassName::functionN()     // do Nth thing
{    }

I assumed this format to allow two different ROS nodes to call and use the same class. I get a compile error (truncated to what i believe is the relevant error codes) :

[100%] Building CXX object CMakeFiles/handrail_end_class.dir/src/handrail_end_class.cpp.o
Linking CXX executable /home/benjamin/r2_hydro/devel_isolated/lib/nasa_r2_vision_handrail/handrail_end_class
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 0 has invalid symbol index 10
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 1 has invalid symbol index 11
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 2 has invalid symbol index 2
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 3 has invalid symbol index 2
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 4 has invalid symbol index 10
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 5 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 6 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 7 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 8 has invalid symbol index 2
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 9 has invalid symbol index 2
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 10 has invalid symbol index 11
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 11 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 12 has invalid symbol index 12
/usr/bin/ld: /usr ...