Create iterator for class using map - c++

Question

I am implementing a class using a map, like so:
class Letras {
typedef std::pair<int, int> p_c;
std::map<char, p_c> bolsa;
public:
...
};
And I'd like to implement the functionality of an iterator, to be used like so:
Letras l;
Letras::iterator it;
for ( it = l.begin(); it != l.end(); ++it )
cout << *it << endl;
So that it prints out the chars from the std::map first component (key).
Thanks in advance.
More information about Letras
Letras is a class that implements a Scrubble-like letter set, the map is used to represent a set of letras (letters in Spanish) like the following:
{{letter_1, {quantity_1, score_1}}, {letter_2, {quantity_2, score_2}}, ..., {letter_n, {quantity_n, score_n}}}
Where letter_i is a certain letter from the set, quantity_i is the amount of times that letter is in the set (a Scrubble-like letter set can have various identical letters) and score_i is the letter score.
I have used a map because a letter can only have an associated score, so that in this class, i != j => letter_i != letter_j.
The utility of Letras is to find the best words formed by a certain letter set from a Diccionario class (dictionary), another class that has implemented a DAWG structure for fast search and lookup.

Answer 1

You can do something like this:
#include <iostream>
#include <map>
#include <algorithm>
using namespace std;
class Letras {
private:
typedef std::pair<int, int> p_c;
std::map<char, p_c> bolsa;
public:
class iterator {
private:
std::map<char, p_c>::iterator it;
public:
iterator(const std::map<char, p_c>::iterator &it) {
this->it = it;
}
// EDIT: Removing Copy Semantics
iterator(const iterator &it) = delete;
iterator &operator =(const iterator &it) = delete;
// EDIT: Enabling Move Semantics
iterator(iterator &&it) = default;
iterator &operator =(iterator &&it) = default;
auto &operator *() const {
return it->first;
}
iterator &operator ++(int) {
this->it++;
return *this;
}
bool operator !=(const iterator &it) {
return this->it != it.it;
}
};
auto begin() {
return iterator(bolsa.begin());
}
auto end() {
return iterator(bolsa.end());
}
void insert(const std::pair<char, p_c> &p) {
bolsa.insert(p);
}
};
int main() {
Letras b;
b.insert(make_pair('f', make_pair(1, 2)));
b.insert(make_pair('g', make_pair(1, 2)));
b.insert(make_pair('h', make_pair(1, 2)));
for (auto it = b.begin(); it != b.end(); it++) {
cout << *it << endl;
}
return 0;
}