Passing member function to another object's member function C++ - c++

Question

I am having issues trying to pass a function as an argument in another object's function. I am well aware there are many similar topics but I either can't get their solution to work or can't understand them.
class foo
{
public:
void func1(void (*Drawing)(void));
template<class T>
void func2(void (T::*Drawing)(void));
};
class bar
{
private:
foo myFoo;
void Drawing();
void func3() {
// Attempt 1
myFoo.func1(Drawing);
// Attempt 2
myFoo.func2<bar>(&bar::Drawing);
}
};
So in my first attempt, I get the error where you can't convert void (bar::*)(void) to void (*)(void) of which I then found out there are normal function pointers and member function pointers.
Attempt 2 was my feeble attempt to overcome this but I get unresolved externals now...
So how can I successfully pass my Drawing() member function into another function from another object?

Answer 1

The issue is that you cannot consider bar::Drawing as a void (*)(void) function since it's a non static method, which therefore required an object (the this context which will be used)
A solution, assuming c++11 is ok for you, would be to use std::bind and to sligtly modify your foo definition:
class foo
{
public:
void func1(std::function<void(void)> Drawing)
{
Drawing(); // or do whatever you want with it
}
};
Then you will be able to do
void bar::func3() {
myFoo.func1(std::bind(&bar::Drawing, this));
}
making valid a lot of potential uses
int main()
{
bar myBar;
myBar.func3();
foo myFoo;
myFoo.func1([](){ printf("test\n"); });
return 0;
}

Answer 2

I'm guessing you've left out important details as to what you're trying to accomplish. However, the following should give you some idea of what you need to do.
Code
#include <iostream>
class foo
{
public:
void func1(void (*Drawing)(void))
{
std::cout << "func1\n";
}
template<class T>
void func2(T* instance, void (T::*fn)(void))
{
std::cout << "func2: ";
(instance->*fn)();
}
};
class bar
{
public:
bar()
{
func3();
}
private:
foo myFoo;
void Drawing()
{
std::cout << "bar::Drawing()\n";
}
void func3()
{
// Attempt 1
//myFoo.func1(Drawing); // This won't work
// Attempt 2
myFoo.func2(this, &bar::Drawing); // Must pass an object instance if you plan to use the member function
}
};
int main(int argc, char *argv[])
{
bar b;
return 0;
}
Sample Output
func2: bar::Drawing()