How do I define a template class and divide it into multiple files?
- by hkBattousai
I have written a simple template class for test purpose. It compiles without any errors, but when I try to use it in main(), it give some linker errors.
main.cpp
#include <iostream>
#include "MyNumber.h"
int wmain(int argc, wchar_t * argv[])
{
MyNumber<float> num;
num.SetValue(3.14);
std::cout << "My number is " << num.GetValue() << "." << std::endl;
system("pause");
return 0;
}
MyNumber.h
#pragma once
template <class T>
class MyNumber
{
public:
MyNumber();
~MyNumber();
void SetValue(T val);
T GetValue();
private:
T m_Number;
};
MyNumber.cpp
#include "MyNumber.h"
template <class T>
MyNumber<T>::MyNumber()
{
m_Number = static_cast<T>(0);
}
template <class T>
MyNumber<T>::~MyNumber()
{
}
template <class T>
void MyNumber<T>::SetValue(T val)
{
m_Number = val;
}
template <class T>
T MyNumber<T>::GetValue()
{
return m_Number;
}
When I build this code, I get the following linker errors:
Error 7 Console Demo C:\Development\IDE\Visual Studio 2010\SAVE\Grand Solution\X64\Debug\Console Demo.exe 1 error LNK1120: 4 unresolved externals
Error 3 Console Demo C:\Development\IDE\Visual Studio 2010\SAVE\Grand Solution\Console Demo\main.obj error LNK2019: unresolved external symbol "public: __cdecl MyNumber::~MyNumber(void)" (??1?$MyNumber@M@@QEAA@XZ) referenced in function wmain
Error 6 Console Demo C:\Development\IDE\Visual Studio 2010\SAVE\Grand Solution\Console Demo\main.obj error LNK2019: unresolved external symbol "public: __cdecl MyNumber::MyNumber(void)" (??0?$MyNumber@M@@QEAA@XZ) referenced in function wmain
Error 4 Console Demo C:\Development\IDE\Visual Studio 2010\SAVE\Grand Solution\Console Demo\main.obj error LNK2019: unresolved external symbol "public: float __cdecl MyNumber::GetValue(void)" (?GetValue@?$MyNumber@M@@QEAAMXZ) referenced in function wmain
Error 5 Console Demo C:\Development\IDE\Visual Studio 2010\SAVE\Grand Solution\Console Demo\main.obj error LNK2019: unresolved external symbol "public: void __cdecl MyNumber::SetValue(float)" (?SetValue@?$MyNumber@M@@QEAAXM@Z) referenced in function wmain
But, if I leave main() empty, I don't get any linker errors.
What is wrong with my template class?
What am I doing wrong?
