Hi again,
I'm a little confused about templates and their implementations. I've read that it's a good idea to put the definitions in the header file, but that makes it so messy. Is there a way to put the implementations in their own cpp file?
I wrote a small test program, but I got an error:
TemplateTest.h
#ifndef TEMPLATE_TEST_H
#define TEMPLATE_TEST_H
template<typename T>
class TemplateTest
{
public:
TemplateTest()
{
}
void setData(const T& data)
{
mData = data;
}
T getData() const
{
return mData;
}
private:
T mData;
};
#endif
#include "TemplateTest.h"
template<typename T>
TemplateTest<T>::TemplateTest()
{
}
template<typename T>
void TemplateTest<T>::setData(const T& data)
{
mData = data;
}
template<typename T>
T TemplateTest<T>::getData() const
{
return mData;
}
#include <iostream>
#include "TemplateTest.h"
using namespace std;
int main()
{
TemplateTest<int> intTest;
intTest.setData(10);
cout << intTest.getData();
}
When I compile it with the definitions in the TemplateTest header file, it works fine. If I comment out those definitions and use the cpp file, I get these errors:
error LNK2019: unresolved external symbol "public: int __thiscall TemplateTest<int>::getData(void)const " (?getData@?$TemplateTest@H@@QBEHXZ) referenced in function _main
1>Main.obj : error LNK2019: unresolved external symbol "public: void __thiscall TemplateTest<int>::setData(int const &)" (?setData@?$TemplateTest@H@@QAEXABH@Z) referenced in function _main
1>Main.obj : error LNK2019: unresolved external symbol "public: __thiscall TemplateTest<int>::TemplateTest<int>(void)" (??0?$TemplateTest@H@@QAE@XZ) referenced in function _main
1>TemplateTest.exe : fatal error LNK1120: 3 unresolved externals
So, two questions:
1. Why do I get these errors when using the cpp file definitions?
2. Is there a way to separate the class/struct/whatever in the header file from the implementation into separate files?
Thanks
Edit - also, what would be a good way to initialize mData to a default value? I'm not sure how to do this because I don't know the type of mData when writing the constructor (obviously).
