Momento - Harsh4999/Design-Patterns GitHub Wiki

Momento

USE

• Whenever we want to store object's state without exposing internal details about the state then we can use momento design patterns.
• like if we want to take a snapshot of our object's state which will help us in implementing undo feature.
• Only object who can read or create snapshot is the object
• Ask state as single sealed object

UML

• Originator: Object who's state we want to store
• Momento: Originator object acts as a stored state
• Care Taker: holder for Momento's object

Implementation

• Find out which state needs to be stored in momento
• We then implement the momento with reqwuirement that it can't be changed & read outside the originator
• Momento should not expose anything
• Only originator can read momento
• Originator should have a method which get current snapshot and return instance of momento
• Another method in originator takes a momento object as args and the originator resets to momento's state