I need some help with a linker error that i solved but i cannot explain why
This is my code beginning with my program.h file:
#pragma once
#include <vector>
#include <string>
#include <fstream>
template<class T> class InputData
{
public:
InputData(std::string);
void storeDataFromSourceFile();
void putDataFromSourceFileIntoVector(std::vector<T>);
private:
void inputLocationOfSourceFile();
void setSourceFileToLocation();
std::vector<T> inputVector;
std::string locationOfInputFile;
std::fstream sourceFile;
};
This was the corresponding program.cpp code:
#include <vector>
#include <string>
#include <fstream>
#include "InputData.h"
template<class T> InputData<T>::InputData(std::string source = "")
{
this->locationOfInputFile = source;
if (locationOfInputFile != "")
this->sourceFile.open(locationOfInputFile);
}
template<class T> void InputData<T>::inputLocationOfSourceFile()
{
std::cout << "Please enter location of source file";
std::cin >> this->locationOfInputFile;
}
template<class T> void InputData<T>::setSourceFileToLocation()
{
if (this->locationOfInputFile == "")
this->inputLocationOfSourceFile();
this->sourceFile.open(this->locationOfInputFile);
}
template<class T> void InputData<T>::storeDataFromSourceFile()
{
T inputElement;
if (this->locationOfInputFile == "")
this->setSourceFileToLocation();
while (this->sourceFile >> inputElement)
this->inputVector.push_back(inputElement);
}
template<class T> void InputData<T>::putDataFromSourceFileIntoVector(std::vector<T> destinationVector)
{
destinationVector = this->inputVector;
}
This is my main function in the main.cpp
#include <string>
#include <iostream>
#include <vector>
#include "InputData.h"
void printVector(std::vector<int> vectorToPrint)
{
for (std::vector<int>::const_iterator i = vectorToPrint.begin(); i != vectorToPrint.end(); ++i)
std::cout << *i << ' ';
}
int main()
{
InputData<int> sourceOfIntegers("Input.txt");
std::vector<int> destinationVector;
sourceOfIntegers.storeDataFromSourceFile();
sourceOfIntegers.putDataFromSourceFileIntoVector(destinationVector);
printVector(destinationVector);
}
When i built the program with visual c++ 2013 these were the errors:
error LNK2019: unresolved external symbol "public: __thiscall InputData<int>::InputData<int>(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >)" (??0?$InputData@H@@QAE@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@Z) referenced in function _main
error LNK2019: unresolved external symbol "public: void __thiscall InputData<int>::storeDataFromSourceFile(void)" (?storeDataFromSourceFile@?$InputData@H@@QAEXXZ) referenced in function _main
error LNK2019: unresolved external symbol "public: void __thiscall InputData<int>::putDataFromSourceFileIntoVector(class std::vector<int,class std::allocator<int> >)" (?putDataFromSourceFileIntoVector@?$InputData@H@@QAEXV?$vector@HV?$allocator@H@std@@@std@@@Z) referenced in function _main
This was resolved by moving the function definitions from the program.cpp to the program.h and everything works.
I have checked online for reasons for this error but for some reasons the explanation for my particular code still eludes me.
Can you please give me a specific explanation of why this has happened?
PS: Also checked What is an undefined reference/unresolved external symbol error and how do I fix it? but still can't find a really logical explanation.
