The memento design pattern
Depending on the software we are writing, we might have a requirement to be able to restore the state of an object back to its previous state. The purpose of the memento design pattern is to:
Note
Provide the ability to execute an undo action in order to restore an object to a previous state.
The original memento design pattern is implemented with the help of three main objects:
Originator: The object whose state we want to be able to restore
Caretaker: The object that triggers the changes to the originator object and uses the memento objects for rollback, if needed
Memento: The object that carries the actual state of the originator and can be used to restore to one of the previous states
It is important to know that the memento object can be handled only by the originator. The caretaker and all other classes can just store it and nothing else.
Class diagram
A classical example of the memento design pattern that comes to mind is text editors. We can always undo whatever...
