How to Pass C Member Function Pointers Correctly?

How to Pass Member Function Pointers in C

When passing a class member function to a function that accepts a member function pointer, it's essential to provide both a pointer to the object and a pointer to the function.

In the given example, the MenuButton::SetButton() function requires a function pointer with a certain signature. To pass a member function, you need to supply both the object pointer (this) and the member function pointer. This can be achieved by modifying MenuButton::SetButton() as follows:

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;
}</class>

Now, the SetButton() function takes both the object pointer and the function pointer as parameters.

In the testMenu class, the member function can be passed like this:

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

This provides the necessary object and member function pointers to the SetButton() function, allowing it to correctly invoke the member function later.

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