Undo and redo are common features in editing software. They look simple on the surface, but how do they work internally? How do you design structure and behavior for them?
Have you had a chance to watch The Spy Gone North? The spy infiltrated North Korea's secret locations, and collected its secrets effectively by applying the Visitor Pattern!
Porsche and Lamborghini are the children of Volkswagen. Their manufacturing process uses the same structure because they both implement the Volkswagen Template Method.
Have you ever thought about the ATM logic? How is ATM logic organized to cover all cases without any misses? Do you feel confused when handling many operations on many states?
Some students in a class are attentive, but others are easily distracted. The teacher is indifferent to them; for her, they are all observers and she just performs her duty.
