The Command Design Pattern encapsulates requests as objects so that different requests can be handled uniformly. A Command defines an interface for executing an operation but delegates the responsibility of performing the operation to an associated receiver object. This allows requests to be parameterized with different receivers, queued or executed at a later time, and supported by undo/redo operations through command history.

1. Command Design Pattern(Action, Transaction)

2. OutlineIntent & MotivationStructureApplicability & ImplementationExamples

3. Intent & MotivationEncapsulate a request as an objectIssue requests without knowing operationeg. Button & MenuItem in a toolkit

4. Basic Structureabstract Command class to define interfaceConcrete implementation links command to receiver

5. Structure

6. Applicability & ConsequencesDecouple invoker and receiverLink same command to multiple invokersMacroCommand: chain commands togetherUndo/Redo: store state and reversal

7. ImplementationCommand intelligenceState InformationReceiver, Arguments, Original Values, Copy CommandBinding OnlyNo Separate Receiver

8. Example…