Question

I have an generic math-method, that operates under a set of functions (with a lot of variables and states, so it can’t be static). I’ve implemented method in parent class and I want to declare a different set of functions in every child-class.
I’ve try to do something like this:

class A {
public:
    typedef int (A::*func)();
    func * fs;
    void f() { /*call functions from this->fs*/ }
};

class B : public A {
public:
    int smth;

    B(int smth) {
         this->smth = smth; //user-provided variables

        //there may be a lot of functions with same interface
        this->fs = new func[1];
        fs[0] = &B::f;
    }

    int f() {
        return smth + 1;
    }
};

It fails with this error:
error C2440: ‘=’ : cannot convert from ‘int (__thiscall B::* )(void)’ to ‘A::func’

Or “IntelliSense: a pointer to a bound function may only be used to call the function” if I try to use &this->f;

Answer 1

Curiously recurring template pattern would help.

template<typename Derived>
class A {
public:
    typedef int (Derived::*func)();
    func * fs;
    void f()
    {
        Derived* const This = static_cast<Derived*>(this);
        /* call functions like (This->*(fs[0]))() */
    }
};

class B : public A<B> {
public:
    int smth;

    B(int smth) {
         this->smth = smth; //user-provided variables

        //there may be a lot of functions with same interface
        this->fs = new func[1];
        fs[0] = &B::f;
    }

    int f() {
        return smth + 1;
    }
};