This is adapted from Alex Martelli's Five Easy Pieces article. See also Singleton? We don't need no stinkin' singleton!, especially the comments.
It's often very useful to avoid passing references to commonly used objects and to avoid the problems inherent in a singleton's dependence on object identity.
Borg provides a simple, lightweight
alternative that maintains a shared state across object instantiations. All that's
required is inheritance, and a simple set up. Originally written around 2001, it
has stood the test of time.
As Alex Martelli is careful to point out, Borg is not a singleton!
See example/borg_example for a sample implementation easily adaptable to your needs.
Note that the shared state is preserved although the object references are different.
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