Creating a template class object using a template constructor

Question

I'm having trouble creating a class object from a template class in which I need the constructor to also be a template and accept a parameter when the object is created. However, when I attempt to create the object, I receive an error message stating that I'm referencing something that doesn't exist.

Here's my code:

using namespace std;
#include <cstdlib>

template <class Node_Type>
class BinaryTree 
{
public:
    BinaryTree(Node_Type);
    BinaryTree(Node_Type, Node_Type);
    BinaryTree(Node_Type, Node_Type, Node_Type);
    bool isEmpty();
    Node_Type info();
    Node_Type inOrder();
    Node_Type preOrder();
    Node_Type postOrder();


private:
    struct Tree_Node
{
    Node_Type Node_Info;
    BinaryTree<Node_Type> *left;
    BinaryTree<Node_Type> *right;
};

Tree_Node *root;

};

#endif

and my .cpp:

template <class Node_Type>
BinaryTree<Node_Type>::BinaryTree(Node_Type rootNode) {

    root = rootNode;
    root->left = NULL;
    root->right = NULL;

}

There's more to the .cpp, but it's just other function members that are irrelevant. My constructor shown above is what I can't get to work.

In my main, I'm attempting to declare my object with the call:

BinaryTree<char> node('a');

but when I try this, I get an error message stating:

undefined reference to `BinaryTree<char>::BinaryTree(char)'

I've been trying to figure this out for two days now. I've Googled every topic I can think of and read countless examples on Stack Overflow and other sources with no help. Can anyone please explain what my problem is? I know how to do my project, and I'd be finished by now if the syntax wasn't so ridiculous in C++. Thanks in advance!

Answer 1

Template code should be visible at the time of instantiation, meaning that the definition of the functions must also be in the header.