1. MVC Nick Lopez Duplication of course material for any commercial purpose without the explicit written permission of the professor is prohibited.

2. Design Patterns so far Simple problems regarding class interactions – Patterns so far involve few classes Are there larger problems that patterns can also support?

3. MVC Model View Controller Divides an application in 3 parts – Model – Views – Controller

4. MVC Provides a mechanism to propagate updates Guarantees consistency between info in the model and the what is presented in views The observer pattern is key

5. Motivation Allows for definition of highly cohesive models Emphasizes business logic over user interface Minimizes impact of changes when the interface evolves

6. Motivation Allows for definition of multiple views over the same model New views can be added without changes to the other components The model can be reused for other interfaces

7. Model Encapsulates the functionality of the application Registers observers Notifies observers of changes in the model Collaborates with views and controllers: – The controller can invoke methods from the model to make changes – The views and controllers get access to data for update

8. Model Application services Get data Notify changes Observer Update *

9. Model Application services Get data Notify changes Observer Update * ViewController

10. View Displays info to the user – Contains an update service activated when the model notifies changes Collaborates with model and controllers: – Obtains data from model – Can provide controllers with data visualizationservices

11. Controllers Receives input from the user Translates user events to service invocations in the model Collaborates with model and views: – The controller can also react to changes in the model (also can behave as a view)

12. Model Application services Get data Notify changes Observer Update * View Controller Update Display information Update Manage events

13. Exercise Does the number trains design implement MVC? Where is the model, views and controllers? – Make changes if necessary to make them explicit

14. Exercise Make changes to include a new view and a new controller Build a sequence diagram showing how views are registered Build a sequence diagram showing – an event from the user (adding a track) from one controller