Question

I’ve only just yesterday figured out function pointers, and I am implementing a console/command system in a game engine.

I figured using a map with a string key and function pointer value would eliminate the need for a huge list of if statements when choosing what to do when running the commands.

I’m getting this error:

argument of type
    "void (Game::*)(std::string prop, std::string param)"
is incompatible with parameter of type
    "void (*)(std::string prop, std::string param)"

Now I think I know what this means. I could use a static function to get round this, but I want to be able to reference a method of a specific instance of Game.

However the map of function pointers must be able to point to any function with return void and 2 string parameters.

Firstly is this possible?

If not, is it somehow possible to modify instance variables through a static member function? I don’t have high hopes for this.

Any help is appreciated as always.

Answer 1

Function pointers are the suck. Don’t ever use them unless you’re absolutely forced to. Instead, prefer std::function<void(std::string, std::string)> and std::bind/lambdas. Unlike function pointers, these can work with any function object, including a bound member function.

std::unordered_map<std::string, std::function<void()>> command_map;
Game game;
Help helper;
command_map["quit"] = [] { exit(); };
command_map["play"] = [&] { game.play(); };
command_map["help"] = [&] { helper.help(); };