December 2016
Intermediate to advanced
841 pages
17h
English
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Memento Pattern
We've talked about an undo support implementation in the previous section on the Command Pattern, and found it was not easy to implement the mechanism purely based on reversing all the operations. However, if we take snapshots of objects as their history, we may manage to avoid accumulating mistakes and make the system more stable. But then we have a problem: we need to store the states of objects while the states are encapsulated with objects themselves.
Memento Pattern helps in this situation. While a memento carries the state of an object at a certain time point, it also controls the process of setting the state back to an object. This makes the internal state implementation hidden from the undo mechanism in the following example: ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.