Suppose I a have a Widget class that is part of a framework used independently by many applications. I create Widget instances in many situations and their lifetimes vary. In addition to Widget's instance specified methods, I would like to be able to perform the follow class wide operations:

• Find a single Widget instance based on a unique id
• Iterate over the list of all Widgets
• Remove a widget from the set of all widgets

In order support these operations, I have been considering two approaches:

1. Container class - Create some container or manager class, WidgetContainer, which holds a list of all Widget instances, support iteration and provides methods for Widget addition, removal and lookup. For example in C#:

   public class WidgetContainer : IEnumerable<Widget>  
   {  
     public void AddWidget(Widget);  
     public Widget GetWidget(WidgetId id);  
     public void RemoveWidget(WidgetId id);  
   }  
   

2. Static class methods - Add static class methods to Widget. For example:

   public class Widget
   {
     public Widget(WidgetId id);
   
     public static Widget GetWidget(WidgetId id);
     public static void RemoveWidget(WidgetId id);
     public static IEnumerable<Widget> AllWidgets();  
   }
   

Using a container class has the added problem of how to access the container class. Make it a singleton?..yuck! Create some World object that provides access to all such container classes?

I have seen many frameworks that use the container class approach, so what is the general consensus?