Question

In some languages (PHP and JavaScript come to mind), I can use a variable as a function. For example:

PHP: Class::$var_function();

Is it possible to this in C++ in a way that doesn’t require a switch or if statement?

Answer 1

James’ answer is probably the best. But, if you’re using a c++11 compatible compiler, you can alternately use std::function

For example:

#include <functional>
#include <iostream>
typedef std::function<void(int a)> callback_t;

class A {
public:
   void fn(int a) { std::cout << a << std::endl; }
};

void fn2(int b) { std::cout << a << std::endl; }

int main() {
   A a;
   callback_t c = std::bind(&A::fn, a, std::placeholders::_1);
   c(1);

   c = fn2;
   c(2);

   return 0;
}

And a boost version (I’ve never used this so it may be wrong):

#include <boost/function.hpp>
#include <iostream>
typedef boost::function<void(int a)> callback_t;

class A {
public:
   void fn(int a) { std::cout << a << std::endl; }
};

void fn2(int b) { std::cout << a << std::endl; }

int main() {
   A a;
   callback_t c = boost::bind(&A::fn, a, boost::placeholders::_1);
   c(1);

   c = fn2;
   c(2);

   return 0;
}