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Question 5(MVC)

a) (10) In the third Clock user interface, a Clock instance forms the model and a ClockText instance forms a view. Describe the sequence of messages that occur when a second of time passes by, such that the Clock is updated and the updated time is displayed by the ClockText. Hints: Think about self changed:, nextSecond, update:, and dependents.


6 points for showing basic knowledge of how the process works
4 points for including the details (message names, senders and receivers)



(b) (5) Why go to all of this trouble? Why not just have the Clock display the correct time at each second?

Use of MVC provides separation of the model and the view, leading to better reusability and maintainability. It also allows multiple views in a single model.

2 points: maintainability, changeability or something of the sort, perhaps a better object design
2 points: enhanced reusability
1 point: multiple views on a single model



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