Problem with copy constructor with class with polymorphic pointers

I have class with two fields witch are pointers to abstract class. How i can write copy constructor witch will copy the data pointed with the two pointers.

Here is the class

class OSGFMenu;
class OSGFMenuItem;
typedef void(OSGFMenu::*OSGFMenuCommand)(OSGFMenuItem*);
typedef int (OSGFMenuItem::*FNMETHOD) ( int, char* );
class OSGFMenuItem:
    public OSGFDrawableComponent
{
public:
    OSGFMenuItem(Game& game,OSGFMenu& menu)
        :OSGFDrawableComponent(game),mMenu(menu),mActive(false)
    {
    }
    OSGFMenuItem(const OSGFMenuItem& menuItem)
        :OSGFDrawableComponent(menuItem),mMenu(menuItem.mMenu)
    {
        Copy(menuItem);
    }
    OSGFMenuItem& operator=(const OSGFMenuItem& menuItem)
    {
        if(&menuItem != this)
            Copy(me开发者_运维知识库nuItem);
        return *this;
    }
    void SetActive(bool active)
    {
        mActive = active;
    }
    void Activate()
    {
        SetActive(true);
    }
    void DeActivate()
    {
        SetActive(false);
    }
    void SetCommand(OSGFMenuCommand command)
    {
        mCommand = command;
    }
    virtual void Render()const
    {
        if(!mActive)
            DrawIfNotNull(mDrawData);
        else
            if(!DrawIfNotNull(mActiveDrawData))
                DrawIfNotNull(mDrawData);

    }
    virtual void Update(double dTime)
    {
        OSGFDrawableComponent* drawData = 
            dynamic_cast<OSGFDrawableComponent*>(mDrawData);
        if(drawData)
            drawData->Update(dTime);
    }
    void Invoke()
    {
        (mMenu.*mCommand)(this);
    }
    ~OSGFMenuItem()
    {
        SafeDelete(mDrawData);
        SafeDelete(mActiveDrawData);
    }
protected:
    void SetDrawData(IDrawable* drawData)
    {
        mDrawData = drawData;
    }
    void SetActiveDrawData(IDrawable* drawData)
    {
        mActiveDrawData = drawData;
    }
private:
    bool DrawIfNotNull(IDrawable* drawData)const
    {
        if(!drawData)return false;
        drawData->Render();
        return true;
    }
    void Copy(const OSGFMenuItem& menuItem)
    {
        mCommand = menuItem.mCommand;
        *mDrawData = *menuItem.mDrawData;
        *mActiveDrawData = *menuItem.mActiveDrawData;
        mActive = menuItem.mActive;
    }
    OSGFMenuCommand mCommand;
    OSGFMenu& mMenu;
    IDrawable* mDrawData;
    IDrawable* mActiveDrawData;
    bool mActive;
};

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The question is whether the objects pointed by the polymorphic pointers have to be copied. If that is the case, the best option would be providing a clone() virtual method in your contained class hierarchy that will create a copy of the object.

struct base {
   virtual base* clone() = 0;
   virtual void foo() = 0;
};
struct derived : base {
   virtual derived* clone() { return new derived(*this); }
   virtual foo();
};
class container {
   base * ptr;
public:
   container( base * p ) : ptr(p) {}
   container( container const & lhs ) : ptr( lhs.ptr->clone() ) 
   {}
};

---

If you need to copy the exact type of the IDrawable hierarchy, I think your only chance is to add a Clone() abstract method to IDrawable interface.

Its signature will be

IDrawable* clone() const;

you may omit const if it needs to modify the object pointed by this.

---

You need a virtual copy constructor to achieve this. Since it is not supported in C++ you can simulate this effect by having a virtual clone method. See What is a "virtual" constructor? for details.

---

Your IDrawable will need some sort of virtual Clone() function.