Command pattern - Behavioral

• Provides an interface to encapsulate a request 
• Allows the parameterization of clients with different requests
• Allows saving the requests in a queue
• Make the interface implemented by subclasses in order to parameterize the clients.

 


How it works ?

• Both an invoker object and several command objects are held by a client object.
• Client knows which command to run.
• Command invokes a method of reciever
• Invoker object knows how to execute a command.
• To execute a command, it passes the command object to the invoker object.

Where to use ?

• One action can be represented in many ways, like drop-down menu, buttons and popup menu.
• Specify and execute the request at different time.
• Decouple the object with its trigger
• Easily to be extensible without touching the old structure.