Mastering Python Design Patterns - Second Edition

Memento pattern

In many situations, we need a way to easily take a snapshot of the internal state of an object, so that we can restore the object with it when needed. Memento is a design pattern that can help us implement a solution for such situations.

The Memento design pattern has three key components:

• Memento, a simple object that contains basic state storage and retrieval capabilities
• Originator, an object that gets and sets values of Memento instances
• Caretaker, an object that can store and retrieve all previously created Memento instances

Memento shares many similarities with the Command pattern.