Command patternSynopsis or Intent:

Command pattern
Synopsis or Intent: Encapsulate a request as an object, thereby letting you parameterize clients with different requests, queue or log requests, and support undoable operations
Context: You want to model the time evolution of a program:
What needs to be done, e.g. queued requests, alarms, conditions for action
What is being done, e.g. which parts of a composite or distributed action have been completed
What has been done, e.g. a log of undoable operations
What are some applications that need to support undo?
Editor, calculator, database with transactions
Perform an execute at one time, undo at a different time
Solution: represent units of work as Command objects
Interface of a Command object can be a simple execute() method
Extra methods can support undo and redo
Commands can be persistent and globally accessible, just lik