Command

This is a UML class diagram example for the Command design pattern.

Purpose

Encapsulates a request allowing it to be treated as an object. This allows the request to be handled in traditionally object based relationships such as queuing and callbacks.

Use When

• You need callback functionality.
• Requests need to be handled at variant times or in variant orders.
• A history of requests is needed.
• The invoker should be decoupled from the object handling the invocation.