The memento pattern
Encapsulation is one of the fundamental principles of object-oriented design. We also know that each class should have a single responsibility. As we add functionality to our object, we might realize that we need to save its internal state to be able to restore it at a later stage. If we implement such functionality directly in the class, the class might become too complex and we might end up breaking the single responsibility principle. At the same time, encapsulation prevents us having direct access to the internal state of the object we need to memorize.
Intent
The memento pattern is used to save the internal state of an object without breaking its encapsulation, and to restore its state at a later stage.
Implementation
The memento pattern relies on three classes: Originator, Memento, and Caretaker, as shown in the following class diagram:
The memento pattern relies on the following classes:
- Originator: The originator is the object for which we need to memorize the state...
