using std::map in a template class, getting LNK2019 link error when creating an object from this template class

[girays]

I have a template class which name is EntityRepositor y and when I
compile this class I get no error. But when I use this class in a main
method I get LNK2019 linking error. std::map object is used in
EntityRepositor y template class. You can see the EntityRepositor y.h and
EntityRepositor y.cpp and main method below:

//EntityRepositor y.h
#pragma once
#ifndef ENTITYREPOSITOR Y_H
#define ENTITYREPOSITOR Y_H

#include <map>

template<class key_type, class val_type>
class EntityRepositor y
{
typedef std::pair<key_t ype, val_typeKeyValP air;
private:
std::map<key_ty pe, val_typereposit ory;
public:
EntityRepositor y(void);
~EntityReposito ry(void);

val_type find(key_type const &key);
void insert(key_type const &key, val_type const &val);
};
#endif
//EntityRepositor y.cpp
#include ".\entityreposi tory.h"

using namespace std;

template<typena me key_type, typename val_type>
EntityRepositor y<key_type, val_type>::Enti tyRepository(vo id)
{
}

template<typena me key_type, typename val_type>
EntityRepositor y<key_type, val_type>::~Ent ityRepository(v oid)
{
}

template<typena me key_type, typename val_type>
val_type EntityRepositor y<key_type, val_type>::find (key_type const
&key)
{
repository::con st_iterator iter = repository.find (key);

if ( iter == repository.end( ) )
{
return NULL;
}

return iter.second();
}

template<typena me key_type, typename val_type>
void EntityRepositor y<key_type, val_type>::inse rt(key_type const &key,
val_type const &val)
{
repository.inse rt( make_pair<key_t ype, val_type>(key, val) );
}
//Program.cpp
#include "EntityReposito ry.h"

int main(int argc, char *argv[])
{
EntityRepositor y<unsigned, doublerep;

rep.insert(0, 1.1);

return 0;
}
If I don't use EntityRepositor y<unsigned, doublerep; and
rep.insert(0, 1.1); (briefly if I don't use EntityRepositor y class) in
main method, it compiles and links successfully but as shown above in
method I get these 3 error messages:

1) error LNK2019: unresolved external symbol "public: void __thiscall
EntityRepositor y<unsigned int,double>::in sert(unsigned int const
&,double const &)" (?insert@?$Enti tyRepository@IN @@QAEXABIABN@Z)
referenced in function _main

2)error LNK2019: unresolved external symbol "public: __thiscall
EntityRepositor y<unsigned int,double>::En tityRepository< unsigned
int,double>(voi d)" (??0?$EntityRep ository@IN@@QAE @XZ) referenced in
function _main

3)error LNK2019: unresolved external symbol "public: __thiscall
EntityRepositor y<unsigned int,double>::~E ntityRepository <unsigned
int,double>(voi d)" (??1?$EntityRep ository@IN@@QAE @XZ) referenced in
function _main
Another important point about this problem is, If I don't seperate the
implementation in a cpp file, otherwise if I implement the class in the
header I get no error.

Does anyone help me about this problem?

Thank in advance...

[Greg]

girays wrote:

I have a template class which name is EntityRepositor y and when I
compile this class I get no error. But when I use this class in a main
method I get LNK2019 linking error. std::map object is used in
EntityRepositor y template class. You can see the EntityRepositor y.h and
EntityRepositor y.cpp and main method below:

//EntityRepositor y.h
#pragma once
#ifndef ENTITYREPOSITOR Y_H
#define ENTITYREPOSITOR Y_H

#include <map>

template<class key_type, class val_type>
class EntityRepositor y
{
typedef std::pair<key_t ype, val_typeKeyValP air;
private:
std::map<key_ty pe, val_typereposit ory;
public:
EntityRepositor y(void);
~EntityReposito ry(void);

val_type find(key_type const &key);
void insert(key_type const &key, val_type const &val);
};
#endif

Another important point about this problem is, If I don't seperate the
implementation in a cpp file, otherwise if I implement the class in the
header I get no error.

A class is implemented in a .cpp file, but a class template should be
implemented in a header file so that its definition is visible to those
source files that instantiate it. Therefore, since EntityRepositor y is
class template (not a class) it should be implemented in
EntityRepositor y.h.

Greg