Using static maps within a class inside different functions: - c++

Question

I have a class like this:
class SelectorFactory
{
public:
static std::map<std::string,int> _creator;
static void registerCreator(std::string& name,int value)
{
//static std::map<std::string,int> _creator;
if(_creator.end() != _creator.find(name))
{
std::cout << "Selector already registered \n";
}
else
{
std::cout << "Entering " <<name<<" in register: \n";
_creator[name]=value;
}
}
static int createSelector(std::string selectorName)
{
//static std::map<std::string,int> _creator;
std::map< std::string , int >::iterator mapIter=_creator.find(selectorName);
if(mapIter==_creator.end())
{
std::cout<<selectorName<<" Not found in the Map \n" ;
return 0;
}
else
{
int selector= mapIter->second;
return selector;
}
}
};
If I uncomment the commented lines above, code is getting compiled but it's not returning any value from createSelector function which is quite obvious.But if I keep them commented, I am getting error as "_creator was not declared in this scope" inside both the functions.
What should I do to rectify this issue.

Answer 1

In order to have -creator instantiated, you must provide a definition for it. Currently, you have only a declaration.
class SelectorFactory
{
static std::map<std::string,Int> _creator;
};
std::map<std::string,Int> SelectorFactory::_creator;

Answer 2

SelectorFactory.h :
#ifndef __SELECTOR_FACTORY__H__
#define __SELECTOR_FACTORY__H__
#include <string>
#include <map>
class SelectorFactory
{
public:
static void registerCreator(std::string& name,int value);
static int createSelector(std::string selectorName);
private: // !!!!!!!!! NOT PUBLIC!!! >:(
static std::map<std::string,int> _creator;
};
#endif // __SELECTOR_FACTORY__H__
SelectorFactory.cpp :
#include "SelectorFactory.h"
#include <iostream>
std::map<std::string,int> SelectorFactory::_creator;
void SelectorFactory::registerCreator(std::string& name,int value)
{
if(_creator.end() != _creator.find(name))
{
std::cout << "Selector already registered \n";
}
else
{
std::cout << "Entering " <<name<<" in register: \n";
_creator[name]=value;
}
}
int SelectorFactory::createSelector(std::string selectorName)
{
std::map< std::string , int >::iterator mapIter=_creator.find(selectorName);
if(mapIter==_creator.end())
{
std::cout<<selectorName<<" Not found in the Map \n" ;
return 0;
}
else
{
int selector= mapIter->second;
return selector;
}
}