The command pattern should be used when:
* You need a command to have a life span independent of the original request, or if you want to queue, specify and execute requests at different times.
* You need undo/redo operations. The command’s execution can be stored for reversing its effects. It is important that the Command class implements the methods undo and redo.
* You need to structure a system around high-level operations built on primitive operations.
The command pattern has several advantages, summarised in the following points:
* It decouples the classes that invoke the operation from the object that knows how to execute the operation.
* It allows you to create a sequence of commands by providing a queue system.
* Implementing extensions to add a new command is easy and can be done without changing the existing code.
* You can also define a rollback system with the Command pattern — like in the Wizard example, we could write a rollback method.
* Have strict control over how and when commands are invoked.
* The code is easier to use, understand and test since the commands simplify the code.