Using Template Class In Separate Class

I have a template class for a tree. Now I want to make a class called TreeIterator that will just iterate through the tree and return a node. Is there a way to include and declare a Tree variable without making TreeIterator also a template? Or would the best option just be to make the iterator a nested class? The code below is what I want to do -

Code:

---

#include "Tree.h"

class TreeIterator {
private:
        Tree tree;
};

#endif

---

But this is what compiles -

Code:

---

#ifndef TREEITERATOR_H
#define TREEITERATOR_H
#include "Tree.h"

template<typename T>
class TreeIterator {
private:
        Tree<T> tree;
};

#endif

---

Any help is appreciated

Why don't you want to make TreeIterator a template?
If it iterates over Tree<T> then it should be a template too.

Code:

---

#ifndef TREE_H
#define TREE_H

template<class T>
struct TreeNode {
private:
    int key;
    // .. etc
};

template<class T>
class TreeIterator {
public:
    TreeIterator(TreeNode<T>* nodePtr): node(nodePtr) { }
    int getKey() { return node->key; }
    bool hasNext() { // implement this }
    void next() { // implement this }

private:
    TreeNode<T>* node; // reference instead of copy
};

template<typename T>
class Tree {
public:
    TreeIterator<T> getIterator()
    {
        return TreeIterator<T>(root);
    }
private:
    TreeNode<T>* root;
};

#endif

---

That's your basic setup for a container class with an iterator type (i.e., STL)

The iterator holds a reference to a TreeNode since you don't want each iterator to make its own copy of a node and since you'll be dealing with Node pointers inside Tree. TreeNode is a struct and not part of the public interface.

Returning straight up nodes is a bad idea. Just use TreeIterator as a proxy class for TreeNode.

Check out the STL source code for a quality implementation.