Question

I have two classes that don’t know anything about themselfs class A, class B.

Class A is called the ENGINE,
Class B is called the GUI.

I want GUI class to have a pointer to a function in class ENGINE, so that when an event occurs on GUIControl, it calls ENGINE member function with two parameters (int,int).

Here’s how i would like to have it:

class CGUIManager
{
public:
    void SetControlCallback(void(*pFunctionPointer)(int,int) );

private:
    void (*m_pControlCallbackFunction)(int,int) ;
};
void CGUIManager::SetControlCallback(void(*pFunctionPointer)(int,int) )
{
    if(pFunctionPointer)
        m_pControlCallbackFunction = pFunctionPointer;
}

class CEngine
{
private:        
    void GUIControlsCallback(int iControlID, int iControlMessage);
    CGUIManager *pGUI;
};

Now while initializing ENGINE, i want to call:

//Set Controls Callback to CEngine Method 
pGUI->SetControlsCallback( GUIControlsCallback );

To register a callback within CGUIManager class, that points to a method in CEngine class.

How can i do that?

Thanks in advance.

Answer 1

I would suggest using an interface (or something like that) if you would like it to be oo instead of function pointers ( which must point to a static member btw )

class IGuiCallback
{
public:
    virtual void  GUIControlsCallback(int iControlID, int iControlMessage)=0;
};

class CGUIManager
{
public:
    void SetControlCallback(IGuiCallback*);

private:
    IGuiCallback* m_pCallback;
};

class CEngine:public IGuiCallback
{
public:
    void GUIControlsCallback(int iControlID, int iControlMessage);

private:
    CGUIManager *pGUI;
};

then in engine:

pGUI->SetCallback(this);

There may be some syntax errors in my code but you should get the picture