How to call a function that is in an array of function pointers?

Question

I have an array that contains function pointers to functions that are inside my GameBoard class. How can I call one of those functions?

class myClass {
    int plusOne(int val) {return val + 1;}
    int minusOne(int val) {return val - 1;}
    int keepTheSame(int val) {return val;}

    int (myClass::*functions[3])(int val) {&myClass::plusOne, &myClass::minusOne, &myClass::keepTheSame};

    // Get coordinates of all positions that flip when placing disc at x,y
    vector<pair<int, int>> getFlipDiscs(pair<int, int> moveCoord, int color) {
        int a = (*functions[0])(2); // error: indirection requires pointer operand
    }
};

I've looked on the internet for member function pointers and arrays of function pointers and found quite a lot of information, but I wasn't able to combine those in a working solution.

Answer 1

Your function pointers are actually pointer to member functionss. To call any of these you’ll need to provide the object of the class you want to call them on. I think this should work:

(this->*(functions[0]))(2);

That said, I recommend not to pursue this direction! Sooner or later you’ll want to register other operations and usin an array of std::function<Signature> objects is more flexible.