---------------------
*** Main Project ***
---------------------
 ->This project generate .exe file

mainProject.h
-------------
class MainProjectHeder{

   virtual void foo() = 0;    // this function is work
   void foo1();              // this function giving me error like unresolved external symbol
   void foo2{                // this work
     print("hello");
   };
};

void MainProjectHeder::foo1(){
     print("function not working");
}


ExperimentFactoryInterface.h
----------------------------
#include <MainProjectHeder.h>

class ExperimentFactoryInterface {
public:
    virtual ~ExperimentFactoryInterface() {}
    virtual MainProjectHeder* CreateExperiment(const QVariant& = QVariant()) = 0;
};



----------------------
  *** Pulgin code  ***
----------------------
->This Project is generate DLL file

Experiment.h
-------------

#include <mainProject.h>
class Experiment : public MainProjectHeder{

      virtual void foo();
};

void Experiment:foo(){
    print("work fine");
}


Factory.h
----------
#include "cyclicvoltammetry.h"
#include <ExperimentFactoryInterface.h>

class Factory : public ExperimentFactoryInterface {
public:
    MainProjectHeder* CreateExperiment(const QVariant& = QVariant());
};


MainProjectHeder* Factory::CreateExperiment(const QVariant&) {
    return new Experiment;
}