Dr. Dobb's Journal September 1998

The Monostate Pattern

Implementation

• Ensuring a unique state for all objects. The crucial step is to declare all data members to be static.
• Mandating local instantiation. Here, the crucial requirement is that no member functions be declared static.
• Subclassing a Monostate class. Implementation of an inheritance hierarchy takes place as for any "ordinary" class and requires no supplementary coding.

Consequences

• Multiple local instantiations but always with only a single state.
• Persistent object state in the absence of any instantiations.
• Familiar syntax. Does not require an accessor function as with Singleton objects.

--S.B. and J.M.C.

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