Pro Design Patterns in Swift

Chapter    23

The Memento Pattern

The memento pattern is a close relative of the command pattern I described in Chapter 20, with the important difference that it is used to capture the complete state of an object so that it can be subsequently reset. Table 23-1 puts the memento pattern in context.

Table 23-1. Putting the Memento Pattern into Context

Question	Answer
What is it?	The memento pattern captures the complete state of an object into a memento that can be used to reset the object at a later date.
What are the benefits?	The memento pattern allows a complete reset of an object without the need to track and apply individual undo commands.
When should you use this pattern?	Use this pattern when there is a “known-good” point in an object’s life ...