Question

I have a parent class which holds a map and n the child class i have used to inherit that class with for some reason can’t access the map which i can’t under stand why, i want to access the values inside the map.

my code is as follows

//HEADER FILE 
#include <iostream>
#include <map>
using namespace std;

//////PARENT CLASS
struct TTYElementBase
{
    //some code here
};

class element
{
    public:

        std::map<char,std::string> transMask;
        std::map<char,std::string>::iterator it;

        void populate();
};

//////CHILD CLASS .HPP

class elementV : public element
{
public :
    std::string s1;
    std::string s2;
    elementV();
    friend ostream &operator<< (ostream &, const elementV &);
    void transLateMask();
};

//CPP FILE 
#include "example.h"
#include <iostream>

elementV::elementV()
{
}

void elementV::transLateMask()
{
    for ( it=transMask.begin() ; it != transMask.end(); it++ )
        cout << (*it).first << endl;
}

int main()
{
    elementV v;
    v.transLateMask();
}

// ' OUTPUT IS NOTHING I DONT KNOW WHY?'

output is nothing but i need to acces the map fron the parent class, what am i doing wrong?

any help i will be very gratefull

Thanks

Answer 1

Does the map contain an entry for 'D' when you call transLateMask()? You’ll get undefined behaviour (perhaps a runtime error) if it doesn’t, since you don’t check the result of find(). Something like this would be more robust:

auto found = transMask.find('D');
if (found == transMask.end()) {
    // handle the error in some way, perhaps
    throw std::runtime_error("No D in transMask");
}

std::string str = found->second;

(If you’re not using C++11, then replace auto with the full type name, std::map<char,std::string>::const_iterator).

Alternatively, C++11 adds an at() method which throws std::out_of_range if the key is not found:

std::string str = transMask.at('D')->second;