How do you pass a member function pointer?

Question

I am trying to pass a member function within a class to a function that takes a member function class pointer. The problem I am having is that I am not sure how to properly do this within the class using the this pointer. Does anyone have suggestions?

Here is a copy of the class that is passing the member function:

class testMenu : public MenuScreen{
public:

bool draw;

MenuButton<testMenu> x;

testMenu():MenuScreen("testMenu"){
    x.SetButton(100,100,TEXT("buttonNormal.png"),TEXT("buttonHover.png"),TEXT("buttonPressed.png"),100,40,&this->test2);

    draw = false;
}

void test2(){
    draw = true;
}
};

The function x.SetButton(...) is contained in another class, where "object" is a template.

void SetButton(int xPos, int yPos, LPCWSTR normalFilePath, LPCWSTR hoverFilePath, LPCWSTR pressedFilePath, int Width, int Height, void (object::*ButtonFunc)()) {

    BUTTON::SetButton(xPos, yPos, normalFilePath, hoverFilePath, pressedFilePath, Width, Height);

    this->ButtonFunc = &ButtonFunc;
}

If anyone has any advice on how I can properly send this function so that I can use it later.

Answer 1

To call a member function by pointer, you need two things: A pointer to the object and a pointer to the function. You need both in MenuButton::SetButton()

template <class object>
void MenuButton::SetButton(int xPos, int yPos, LPCWSTR normalFilePath,
        LPCWSTR hoverFilePath, LPCWSTR pressedFilePath,
        int Width, int Height, object *ButtonObj, void (object::*ButtonFunc)())
{
  BUTTON::SetButton(xPos, yPos, normalFilePath, hoverFilePath, pressedFilePath, Width, Height);

  this->ButtonObj = ButtonObj;
  this->ButtonFunc = ButtonFunc;
}

Then you can invoke the function using both pointers:

((ButtonObj)->*(ButtonFunc))();

Don't forget to pass the pointer to your object to MenuButton::SetButton():

testMenu::testMenu()
  :MenuScreen("testMenu")
{
  x.SetButton(100,100,TEXT("buttonNormal.png"), TEXT("buttonHover.png"),
        TEXT("buttonPressed.png"), 100, 40, this, test2);
  draw = false;
}