Singleton Menu!

[ArlexBee-871RBO]

Greetings.

I have subclassed QPushButton, and I'll call it MyPushButton here. Each MyPushButton widget also has a menu associated with it, and I'll call that class NodeMenu. MyPushButton widgets are organized in a custom window, and the user has the ability to split the window unlimited number of times, which in turn creates a new set of MyPushButton widgets of the same kind.

Instead of dynamically creating a new NodeMenu for each MyPushButton widget of the same kind, I figured I should rewrite the NodeMenu class as a singleton. This is what it looks like in short:

class NodeMenu : public QMenu{
 
public:
  typedef enum {MenuAnimation, MenuTransformers, MenuFractals, MenuColor} MenuType;
 
  static NodeMenu *CreateMenu(MenuType menuType){
 
    switch( menuType ){
    case MenuAnimation:
      static NodeMenu animationMenu(menuType);
      return &animationMenu;
 
    case MenuTransformers:
      static NodeMenu transformersMenu(menuType);
      return &transformersMenu;
 
    case MenuFractals:
      static NodeMenu fractalsMenu(menuType);
      return &fractalsMenu;
 
    case MenuColor:
      static NodeMenu colorMenu(menuType);
      return &colorMenu;
    }
  }
 
private:
  NodeMenu(MenuType menuType);
  NodeMenu(const NodeMenu &);
  NodeMenu &operator=(const NodeMenu &);
  ~NodeMenu();
};

class NodeMenu : public QMenu{

public:
  typedef enum {MenuAnimation, MenuTransformers, MenuFractals, MenuColor} MenuType;

  static NodeMenu *CreateMenu(MenuType menuType){

    switch( menuType ){
    case MenuAnimation:
      static NodeMenu animationMenu(menuType);
      return &animationMenu;

    case MenuTransformers:
      static NodeMenu transformersMenu(menuType);
      return &transformersMenu;

    case MenuFractals:
      static NodeMenu fractalsMenu(menuType);
      return &fractalsMenu;

    case MenuColor:
      static NodeMenu colorMenu(menuType);
      return &colorMenu;
    }
  }

private:
  NodeMenu(MenuType menuType);
  NodeMenu(const NodeMenu &);
  NodeMenu &operator=(const NodeMenu &);
  ~NodeMenu();
};

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Now, this works fine, except I can't pass a QWidget *parent to the NodeMenu because if the very first created window is destroyed, then parent becomes a dangling pointer and I get seg-fault.

The NodeMenu doesn't seem to need a parent here, and the singleton gets destroyed during exit. But I would like to ask if anyone thinks there is anything wrong with this approach? I do save little bit of memory this way, but could this approach cause problems later on?

[high_flyer]

I figured I should rewrite the NodeMenu class as a singleton.

How come?

If you need multiple instances of your button, then Singleton is exactly what you DON'T need.

[ArlexBee-871RBO]

How come?

If you need multiple instances of your button, then Singleton is exactly what you DON'T need.

I do need multiple instances of the button, but not the menu. Only one menu is shown at any given time.

[high_flyer]

Sorry, I wrongly understood that you made your button a singleton.
How about using QAction instead of QMenu as base class?
I think that conceptually it is more correct.
Also, QAction is not a gui element, which makes it independent of any existing GUI elements, thus, instead giving it widgets, you give it to widgets.