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; }