I get an error in my program saying "Unresolved External symbol", i tried everything i know but couldn't solve it. I started getting this error after i used class template.
Here is FileHandler Class Header :-
#include <string>
#include <iostream>
#include "test.h"
#include <iomanip>
#include "Administrator.h"
#ifndef  FileHandler_h
#define FileHandler_h
using namespace std;
template<class T>
class FileHandler
   {
     public:string writeToFile(T writeObject);
public: FileHandler();
   };
  #endif
File Handler Class Implementation
template<class T>
FileHandler<T>::FileHandler(){}
template<class T>
string FileHandler<T>:: writeToFile(T writeObject)
{
   ofstream outputFile;
   outputFile.open("file.txt",ios::out|ios::app);
more code..........
     return "done";
 }
Here is the code where i call the method in filehandler class
string Administrator::registerNewMember(Administrator newAdmin)
{
  FileHandler<Administrator> f1;
    return f1.writeToFile(newAdmin);
}
Below is a screen shot of the error which i get.

How do i fix this error?
 
     
     
    