MonoState

Also known as

Borg

Intent

Enforces a behaviour like sharing the same state amongst all instances.

Class diagram

Applicability

Use the Monostate pattern when

• The same state must be shared across all instances of a class.
• Typically this pattern might be used everywhere a Singleton might be used. Singleton usage however is not transparent, Monostate usage is.
• Monostate has one major advantage over singleton. The subclasses might decorate the shared state as they wish and hence can provide dynamically different behaviour than the base class.

Typical Use Case

• The logging class
• Managing a connection to a database
• File manager

Real world examples

Yet to see this.