Accessing a Private struct from child class - c++

Question

I am required to implement these two methods in this class. Elem& operator*() and Elem* operator->(). The only issue whoever is that the Iterator class is defined within a Map Class. While the Elem is defined in the private section of the parent class. The catch is that I am not allowed to modify the the .h file of the class.
class Iterator{
public:
Iterator(){}
explicit Iterator(Elem *cur):_cur(cur) {}
Elem& operator*();
Elem* operator->();
// Iterator operator++(int);
bool operator==(Iterator it);
bool operator!=(Iterator it);
private:
Elem* _cur;
};
Here is my attempted implemnetation of the function. However does not work as it says the struct is private.
Map::Elem& Map::Iterator::operator*(Iterator it){
//do stuff
}
The class is defined within another class. Which the struct is defined in under the private section. I am not really sure how I am supposed to be returning an Elem& or Elem* from within the Iterator class, if the Elem structure is private. However I suspect it has something to do with the Elem* _cur; defined within the private function of the Iterator class.
Here is the struct defined within the Map class. If that makes sense.. its private...
private:
struct Elem {
KEY_TYPE key;
VALUE_TYPE data;
Elem *left;
Elem *right;
};
Elem *_root; // a dummy root sentinel
int _size;
In case what I included does not work, here is the full class definition. Just wanted to include the examples above to include less code.
#ifndef MAP_H
#define MAP_H
#include <iostream>
#include <string>
using namespace std;
typedef string KEY_TYPE;
typedef string VALUE_TYPE;
class Map{
struct Elem; //declaration of an interal structure needed below...
public:
//---Constructors and destructors---
Map(); // constructs empty Map
Map(const Map &rhs); // copy constructor
~Map(); // destructor
// assignment operator
Map& operator=(const Map &rhs);
// insert an element; return true if successful
bool insert(KEY_TYPE, VALUE_TYPE);
// remove an element; return true if successful
bool erase(KEY_TYPE);
// return size of the Map
int size() const;
// return an iterator pointing to the end if an element is not found,
// otherwise, return an iterator to the element
class Iterator;
Iterator find(KEY_TYPE) const;
// Iterators for accessing beginning and end of collection
Iterator begin() const;
Iterator end() const;
// overloaded subscript operator
VALUE_TYPE& operator[](KEY_TYPE);
// output the undering BST
ostream& dump(ostream& out) const;
// a simple Iterator, won't traverse the collection
class Iterator{
public:
Iterator(){}
explicit Iterator(Elem *cur):_cur(cur) {}
Elem& operator*();
Elem* operator->();
// Iterator operator++(int);
bool operator==(Iterator it);
bool operator!=(Iterator it);
private:
Elem* _cur;
};
private:
struct Elem {
KEY_TYPE key;
VALUE_TYPE data;
Elem *left;
Elem *right;
};
Elem *_root; // a dummy root sentinel
int _size;
// helper method for inserting record into tree.
bool insert(Elem *& root, const KEY_TYPE& key, const VALUE_TYPE& data);
// helper method for print tree
void printTree(ostream& out, int level, Elem *p) const;
// common code for deallocation
void destructCode(Elem *& p);
// common code for copy tree
void copyCode(Elem* &newRoot, Elem* origRoot);
};
ostream& operator<< (ostream&, const Map&);
#endif
Any help would be awesome. Been making the rounds on google with no such luck.

Answer 1

The issues is not that Elm is private. Change
Map::Elem& Map::Iterator::operator*(Iterator it){
//do stuff
}
to
Map::Elem& Map::Iterator::operator*(){
//do stuff
}
because the former does not match the signature declared in the header. That causes the defined operator overload to not be in the scope of the class.