How to pass a map from a class constructor to another function in the class

Question

I need to pass the map, mainMap, that I created at the bottom of my huffman_tree::huffman_tree constructor to the function get_character_code() so I can use its contents in that function.

I do not have access to the main function because our teacher is using a driver program to test if our code works or not.

I am new to programming in general so if I worded something weird I apologize.

#ifndef _HUFFMAN_TREE_H_
#define _HUFFMAN_TREE_H_

#include <iostream>

class huffman_tree {
    public:
        huffman_tree(const std::string &file_name);
        ~huffman_tree();

        std::string get_character_code(char character) const;
        std::string encode(const std::string &file_name) const;
        std::string decode(const std::string &string_to_decode) const;  
};

#endif



huffman_tree::huffman_tree(const std::string &file_name)
{
    int count[95] = { 0 };
    int x;

    ifstream inFile(file_name);

    stringstream buffer;
    buffer << inFile.rdbuf();
    string text = buffer.str();

    inFile.close();

    int length = text.length();


    for (int i = 0; i < length; i++)
    {

        if (text[i] >= ' ' && text[i] <= '~')
        {
            x = text[i] - ' ';
            count[x]++;
        }
    }

    int temp[95][2] = { 0 };
    int numbers = 0;

    for (int i = 0; i < 95; i++)
    {

        if (count[i] > 0)
        {
            temp[numbers][0] = count[i];
            temp[numbers][1] = (i + ' ');
            numbers++;
        }
    }

    vector<char> characters;
    vector<int> frequency;

    for (int i = 0; i < numbers; i++)
    {
        frequency.push_back(temp[i][0]);
        characters.push_back((char)(temp[i][1]));
    }

    map<char, string> mainMap;
    mainMap = HuffmanCodes(characters, frequency, numbers);

}


std::string huffman_tree::get_character_code(char character) const 
{

    for (itr = mainMap.begin(); itr != mainMap.end(); ++itr)
    {
        if (itr->first == character)
        {
            return itr->second;
        }
    }

    return "";
}

Answer 1

map<char, string> mainMap; should be a member of your class. That'll allow you to access it from any member function in the class.

class huffman_tree {
public:
    huffman_tree(const std::string& filename);
    ~huffman_tree();

    std::string get_character_code(char character) const;
    std::string encode(const std::string& filename) const;
    std::string decode(const std::string& string_to_decode) const;  
private:
    std::map<char, std::string> mainMap;
};