Question

Implement message passing using hash table or dictionary that maps constant strings to function pointers in java or c++ or python programming language.

Provide well documented working code.

Hint:Assign message names to constant strings and implement constant as keys that maps to function pointers.

Answer 1

Code:

#include <iostream>
#include <functional>
#include <map>

using namespace std;

//MESSAGE DECLARATION
const string BUTTON_CLICk = "Button_Clicked";
const string MOUSE_CLICk = "MButton_Clicked";
const string KEY_CLICk = "KButton_Clicked";
const string MOUSE_RMB_CLICk = "MRMB_Clicked";

//Message Handlers
void onButtonCLicked()
{
   cout << "\nMouse Button Clicked";
}

void onMButtonCLicked()
{
   cout << "\nMouse MButton Clicked";

}
void onKButtonCLicked()
{
   cout << "\nKey Button Clicked";

}

void onMouseRMBCLicked()
{
   cout << "\nMouse RMB Button Clicked";

}

//Process Message function
void processMessage(std::map<string, std::function<void()>>& aMap,const string command)
{
   //Invocation of the respective Handler function
   aMap[command]();
}

int main()
{
   //Assigning the map with the message and corresponding handlers
   std::map<string, std::function<void()>> mapofMessageHandlers;

   mapofMessageHandlers[BUTTON_CLICk] = onButtonCLicked;
   mapofMessageHandlers[MOUSE_CLICk] = onMButtonCLicked;
   mapofMessageHandlers[KEY_CLICk] = onKButtonCLicked;
   mapofMessageHandlers[MOUSE_RMB_CLICk] = onMouseRMBCLicked;

   processMessage(mapofMessageHandlers,MOUSE_CLICk);
}

OUTPUT: