I'm trying to figure out a way of how to be able to assign a function pointer to functions with different number of arguments.
I have a while loop which takes a number of different functions as a conditional statement, so instead of writing multiple while loops with exactly the same code inside I'd like to have one with a function pointer. All the functions are of format bool f(...)
. I think some code will best illustrate what I mean:
int a, b, c, d;
MyClass* my_class;
typedef bool (MyClass::*my_fun_t)();
my_fun_t my_fun;
if (condition1)
my_fun = &MyClass::function_one();
else if (condition2)
my_fun = &MyClass::function_two(a, b);
else if (condition3)
my_fun = &MyClass::function_three(a, b, c);
else if (condition4)
my_fun = &MyClass::function_four(a, b, c, d);
while ((my_class->*my_fun)())
{ ... }
Now this obviously doesn't work because the functions have different signatures. Is it at all possible to make it work in a similar fashion? Are functoids something I should look at?
You could use std::function<>
and std::bind()
.
#include <functional>
using std::placeholders::_1;
typedef std::function<bool(MyClass&)> my_fun_t;
my_fun_t my_fun;
if (condition1)
my_fun = std::bind(&MyClass::function_one, _1);
else if (condition2)
my_fun = std::bind(&MyClass::function_two, _1, a, b);
else if (condition3)
my_fun = std::bind(&MyClass::function_three, _1, a, b, c);
else if (condition4)
my_fun = std::bind(&MyClass::function_four, _1, a, b, c, d);
while (my_fun(my_class)) { ... }
These assumes you will use C++11. If you can't use C++11 but can use TR1, replace all std::
with std::tr1::
. There is also a Boost implementation.