Understanding the Command design pattern

The Command pattern works with the following terms—Command, Receiver, Invoker, and Client:

• A Command object knows about the Receiver objects and invokes a method of the Receiver object.

• Values for parameters of the receiver method are stored in the Command object

• The invoker knows how to execute a command

• The client creates a Command object and sets its receiver

The main intentions of the Command pattern are as follows:

• Encapsulating a request as an object

• Allowing the parameterization of clients with different requests

• Allowing to save the requests in a queue (we will talk about this later in the chapter)

• Providing an object-oriented callback

The Command pattern can be used in the following multiple scenarios:

• Parameterizing objects depending on the action to be performed

• Adding actions to a queue and executing requests at different points

• Creating a structure for high-level operations that are based on smaller operations

The following Python code implements the...