C++ function accepting function pointer and non-static member function as parameter - c++

Question

I built an interface taking pointers to functions. Sometimes this calculation depends on state, which I want to encapsulate in a class and pass its method:
#include <iostream>
class Printer {
public:
static void print(int i) { // Want to get rid of the static
std::cout << i << "\n";
}
};
template<typename int_func>
void with_1(int_func func) {
func(1);
}
int main(int argc, char const *argv[]) {
Printer printer;
with_1(printer.print);
return 0;
}
I need non-static methods (and would even prefer overloading operator()). However removing the static results in error: a pointer to a bound function may only be used to call the function.
I could use a dummy like this:
Printer printer;
void dummy(int i) {
printer.print(i);
}
int main(int argc, char const *argv[]) {
with_1(dummy);
return 0;
}
But that does not look elegant to me. Can I write a template that accepts both, function pointers and non-static methods? Or is there even a better design pattern for my problem?

Answer 1

You can not simply pass non-static method like this, because they work on instance. A simply solution is to use lambda:
#include <iostream>
class Printer {
public:
static void print(int i) { // Want to get rid of the static
std::cout << i << "\n";
}
};
template<typename int_func>
void with_1(int_func func) {
func(1);
}
int main(int argc, char const *argv[]) {
Printer printer;
// Can use capture by reference because we are sure printer still
// exist during execution of with_1
with_1([&printer](int i){ printer.print(i); });
return 0;
}
example

Answer 2

Try this:
int main(int argc, char const *argv[]) {
Printer printer;
with_1( std::bind( &Printer::print, printer, std::placeholders::_1 ) );
return 0;
}
(You'll need to #include <functional>.)