What is the simplest way to create and call dynamically a class method in C++?

Question

I want to fill a map with class name and method, a unique identifier and a pointer to the method.

typedef std::map

        

Answer 1

If you do not want to use member function pointers, you can use statics which take an argument of the class instance. For example:

class MyClass
{
    public:
        void function();

        static void call_function(MyClass *instance);  // Or you can use a reference here.
};

MyClass instance;
MyClass::call_function(&instance);

This requires more work on the coder and causes maintainability issues (since if you update the signature of one, you must update that of the other as well).

You could also use a single static function which calls all your member functions:

class MyClass
{
    public:
        enum Method
        {
            fp_function,
        };

        void function();

        static void invoke_method(MyClass *instance, Method method);  // Or you can use a reference here.
};

void MyClass::invoke_method(MyClass *instance, Method method)
{
    switch(method)
    {
        default:
            // Error or something here.
            return;

        case fp_function:
            instance->function();
            break;

        // Or, if you have a lot of methods:

#define METHOD_CASE(x) case fp_##x: instance->x(); break;

        METHOD_CASE(function);

#undef METHOD_CASE
    }

    // Free logging!  =D
}

MyClass instance;
MyClass::invoke_method(instance, MyClass::fp_function);