// tree.h
#ifndef TREE_H
#define TREE_H

#include <map>
#include <vector>
#include <string>

class First;
class Tree{
  public:
    Tree() {}
    ~Tree() {}
    template<class TF> // where TF is a ConcreteFirst
    void addFirstToTree();
  private:
    std::map<std::string, First *> firstCollection; // <- "First"'s here
};
#include "tree.tpp"

#endif // TREE_H

// tree.tpp
#ifndef TPP_TREE
#define TPP_TREE

#include "tree.h"

template <class TF> // where TF is a ConcreteFirst
void Tree::addFirstToTree(){
  this->firstCollection[TF::name] = new TF(this);
}


#endif // TPP_TREES

// first.h
#ifndef FIRST_H
#define FIRST_H

class Tree;
class First{
  public:
    static const std::string name;
    First(const Tree *baseTree) : myTree(baseTree) {}
    virtual ~First();
  protected:
    const Tree *myTree;
};

template <typename Type> class TypedFirst : public First{
  public:
    static const std::string name;
    TypedFirst(const Tree *baseTree) : First(baseTree) {}
    Type &value();
  private:
    Type _value;
};

#endif // FIRST_H

// first.tpp
#ifndef TPP_FIRST
#define TPP_FIRST

#include "first.h"

template <typename Type>
const std::string TypedFirst<Type>::name = "default typed";
template <typename Type>
Type& TypedFirst::value() {return this->_value;}

#endif // TPP_FIRST

// first.cpp
#include "first.h"

First::~First() {}
const std::string First::name = "default";

// concretefirsta.h
#ifndef CONCRETEFIRSTA_H
#define CONCRETEFIRSTA_H

#include "first.h"
class ConcreteFirstA : public TypedFirst<int>{
  public:
    static const std::string name;
    ConcreteFirstA(const Tree *baseTree);
    virtual ~ConcreteFirstA();
};

#endif // CONCRETEFIRSTA_H

// concretefirsta.cpp
#include "concretefirsta.h"

const std::string ConcreteFirstA::name = "firstA";
ConcreteFirstA::ConcreteFirstA(const Tree* baseTree) : TypedFirst<int>(baseTree) {}
ConcreteFirstA::~ConcreteFirstA() {}

// main.cpp
#include "tree.h"
#include "first.h"

#include "concretefirsta.h"

using namespace std;

int main()
{
    Tree *myTree = new Tree();
    myTree->addFirstToTree<ConcreteFirstA>();
    delete myTree;
    return 0;
}