Template + Multifile

Hi friends
I wrote some program with structue like this :
but it does'nt work , and I don't know why
please help me , Thank you

main.cpp

Code:

---

#include "Unit10.h"
#include <conio.h>

int main(int argc, char* argv[])
{
        tst<int> obj(10);
        obj.show();
        getch();
        return 0;
}

---

Implement (Unit9.cpp) :

Code:

---

#include <iostream>
using std::cout ;

#include "Unit10.h"
template <typename T>
void tst<T>::show()
{
        cout << i ;
}

---

and interface:

Code:

---

#ifndef Unit10H
#define Unit10H
template <typename T>
class tst
{
        public :
                T i ;
                tst<T>(T n=0) : i(n) {}
                void show() ;

};
#endif

---

error :

Code:

---

[Linker Error] Error: Unresolved external 'tst<int>::show()' referenced from C:\UNIT9.OBJ

---

and I checked it in C++Builder , dm , DevC++
but the result of all of them were similar.

Most compilers don't support template function defintions in a separate file (the two you've mentioned definitely don't). Move the template function definition into the header file, Unit10.h

As an aside, take a look at this faq, too.