Link List Help, Iterator Issues - c++

Question

So I have to create a linked list for class and I am stuck with my List::Current() function. For some reason I'm getting a handling error when I try to call the function.
List.h
class List {
private:
struct Node {
int data;
Node* next;
Node() : next(NULL){} //define our own default constructor
Node(int data) : next(NULL), data(data){}
};
typedef struct Node* NodeRef;
NodeRef head;
NodeRef tail;
NodeRef iterator; //points to one node at a time
int size;
public:
int current();
List.cpp
// initialize the values when they are instantiated
List::List() : head(NULL), tail(NULL), iterator(NULL), size(0)
{}
int List::current() {
return iterator->data;
}
void List::push_front(int data) //Inserting a new node in the front of the list
{
if (size == 0) //If there is no nodes in the list, execute the if statement
{
head = new Node(data); //create a new node, and have head point to it
iterator = tail = head; //have tail point to the new node also.
}
else //If there are nodes in the list, execute the else statement
{
NodeRef newNode = new Node(data); //create a new node
newNode->next = head; //have the next pointer point to the head of the next node.
head = newNode; //have the head pointer point to the new node inserted at the beginning of the list
}
size++; //Increment the size counter
}
void List::push_back(int data) //Inserting a node at the end of a list
{
if (size == 0) //If there are no nodes in the list, execute the if statement
{
tail = new Node(data); //Create a new node and have the tail pointer point to it.
iterator = head = tail; //Have the head pointer point to the new node also.
}
else //If there is atleast 1 node in the list, execute the else statement
{
NodeRef newNode = new Node(data); //Create a new node
tail->next = newNode; //Have the tail
tail = newNode; //Have the tail pointer point to the new node.
newNode->next = NULL;
}
size++;
}
void List::begin() //Set the iterator to the head of the list
{
iterator = head;
}
void List::scroll() //Allows us to scroll through the list
{
if (iterator == NULL)
cout << "Iterator is pointing to null" << endl;
else
iterator = iterator->next;
}
LinkedList.cpp
#include "stdafx.h"
#include "List.h"
#include <iostream>
using namespace std;
int _tmain(int argc, _TCHAR* argv[]) {
List B; //Create a new list
B.push_front(5);
B.push_front(4);
B.push_front(3);
B.push_back(10);
cout << B.current() << endl;
system("PAUSE");
return 0;
}
I left some code out because I didn't think listing the other functions that worked properly were necessary to get the point across. If you would like everything I could post that.
I think this solved my issues.

Answer 1

Your issue is you aren't setting iterator.
Personally I wouldn't include it as part of the class and have something like begin() or head() which retrieves an iterator class instance with the head pointer. Then the current and iteration methods would be a part of your iteration class.
But for your current design you could check in push_front to see if the iterator is NULL, and if so set it equal to head. Or you could have a begin_iteration method which sets it to the head, which would also allow you to do more than one iteration through the list.
Edit
Now that you have revealed your entire implementation, you need to set iterator in 2 places. At the end of push_front, and if there is no head in push_back. In other words anywhere you set head, you need to set iterator.
Also how do you move iterator forward? Can you restart the iteration?