Abstract Factory Design Pattern GOF Book example

APF2.cpp

class WidgetFactory{
public:  
    virtual ScrollBar *createScrollBar() = 0;
    virtual Window *createWindow() = 0;
};

class Window{
public:  
    virtual void Paint() = 0;
};

class ScrollBar{
public:  
    virtual void Paint() = 0;
};

class MotifScrollBar() : public ScrollBar{
public:  
    void paint(){
        std::cout << "MotifScrollBar";
    }
};

class PMScrollBar() : public ScrollBar{
public:    
    void paint(){
        std::cout << "PMScrollBar";
    }  
};

class MotifWindow() : public Window{
public:  
    void paint(){
        std::cout << "MotifWindow";
    }
};

class PMWindow() : public Window{
public:      
    void paint(){
        std::cout << "PMWindow";
    }
};

class MotifWidgetFactory : public WidgetFactory{
public:    
    ScrollBar *createScrollBar(){
        return new MotifScrollBar();
    }

    Window *createWindow(){
        return new MotifWindow();
    }
};

class PMWidgetFactory : public WidgetFactory{
public:      
    ScrollBar *createScrollBar(){
        return new PMScrollBar();
    }

    Window *createWindow(){
        return new PMWindow();
    }
};

enum appearanceStds{ PM, Motif};

void main(){

    // var appearance = Settings.Appearance;

    WidgetFactory *factory;

    appearanceStds appearanceChoice = PM;

    switch (appearanceChoice)
    {
        case PM:
            factory = new PMWidgetFactory();
            break;
        case Motif:
            factory = new MotifWidgetFactory();
            break;
        default:
            cout << "This Appearance doesn't exist\n";
    }

    ScrollBar *s = factory->createScrollBar();
    s->paint();

    Window *w = factory->createWindow();
    w->paint();
}