1. Model View Controller Pattern Patterns Model-View-Controller

2. A Single Class T result = I; T nextValue = getNextValue() while (!isSentinel(nextValue)) { result = f(result, nextValue); nextValue = getNextValue(..); } Folding Intra-Class Pattern Loan, int new ALoan(0), 1 ALoan.add(), * >= 0

3. Scanning Inter-Class Pattern Scanner Instance Enumeration Interface Scanner User public interface Enumeration { public nextElement(); public boolean hasMoreElements(); }

4. Architectural Pattern Christopher 79 –Each pattern is a three part rule, which expresses a relation between a certain context, a problem, and a solution. –Each pattern describes a problem which occurs over and over again in our environment, and then describes the core of a solution to that problem, in such a way that you can use this solution a million times over

5. Book on Design Patterns

6. MVC Pattern Model: APointHistoryModel instance Controller: AConsoleController instance Controller: AnAWTController instance Controller: AnAWTController instance Controller: ASwingController instance View: AConsoleView instance View: ABarChartView instance View: APlotterView instance View: Aplotterview instance

7. Displaying Points

8. Swing button AWT button Swing Detachable Toolbar

9. Displaying Points All four views displayed concurrently and kept in Sync.

10. ObjectEditor-based Structure APointHistory ObjectEditor

11. Reusing Point History APointHistory User Interface Code: Single Main Class

12. More Modular Approach Editor: AConsoleEditor Editor: ASwingPlotterEditor Editor: ABarChartEditor Editor: AnAWTPlotterEditor Composer: Single Main Class APointHistory

13. Sharing the View

14. Sharing the Controller

15. Controller Without View

16. View Without Controller

17. Monolithic Editor AWT Plotter Editor APointHistory

18. Separate View and Controller Controller: AnAWTController View: ABarchartView APointHistory addElement( ) size( ) elementAt( ) Performs InputPerforms Output Write methods Read methods

19. Multiple Views and Controllers APointHistory Controller: AConsoleController Controller: AnAWTController Controller: AnAWTController Controller: ASwingController View: AConsoleView View: ABarChartView View: APlotterView View: APlotterView Syncing Controllers and Views?

20. Model View Controller Framework Model: APointHistoryModel Controller: AConsoleController Controller: AnAWTController Controller: AnAWTController Controller: ASwingController View: AConsoleView View: ABarChartView View: APlotterView View: APlotterView Changed object notifies views Listenable Listeners

21. Model View Controller Framework Model: APointHistoryModel Controller: AConsoleController Controller: AnAWTController Controller: AnAWTController Controller: ASwingController View: AConsoleView View: ABarChartView View: APlotterView View: APlotterView Composer: Single Main Class Composer connects models, views, controllers

22. Class Vs Instance Model: APointHistoryModel Controller: AConsoleController Controller: AnAWTController Controller: AnAWTController Controller: ASwingController View: AConsoleView View: ABarChartView View: APlotterView View: APlotterView Composer: Single Main Class Different State

23. MVC Framework Model: APointHistoryModel Instance Controller: AConsoleController instance Controller: AnAWTController instance Controller: AnAWTController instance Controller: ASwingController instance View: AConsoleView instance View: ABarChartView instance View: APlotterView instance View: APlotterView instance Composer: Single Main Class

24. Model Model: APointHistoryModel Instance Controller: AConsoleController instance Controller: AnAWTController instance Controller: AnAWTController instance Controller: ASwingController instance View: AConsoleView instance View: ABarChartView instance View: APlotterView instance View: APlotterView instance Composer: Single Main Class

25. Model Vs PointHistory APointHistory Instance Controller: AConsoleController instance Controller: AnAWTController instance Controller: AnAWTController instance Controller: ASwingController instance View: AConsoleView instance View: ABarChartView instance View: APlotterView instance View: APlotterView instance Composer: Single Main Class

26. Reusing PointHistory PointHistory APointHistory IMPLEMENTS APointHistory Model EXTENDS PointModel EXTENDS IMPLEMENTS

27. Notification Scheme Model: APointHistoryModel Instance View: AConsoleView instance View: ABarChartView instance View: APlotterView instance View: APlotterView instance Each view is registered with model. Each write method in model calls a notification method in each view. Notification method updates display. Model: PointModel Instance (Animating Point) Each student is registered with professor’s listserv. When web page is updated mail sent to students. Student reads web page.

28. View with Multiple Models APointHistoryModel Instance PointModel Instance

29. General Notification Scheme Model: APointHistoryModel Instance View: AConsoleView instance View: ABarChartView instance View: APlotterView instance View: APlotterView instance View may have multiple models with common notification method. Notification method parameter indicates which model. Model: PointModel Instance (Animating Point)

30. PointHistoryModel & PointHistoryListener public interface PointHistoryModel extends PointHistory { public void addListener (PointHistoryListener pointHistoryListener); public void removeListener (PointHistoryListener pointHistoryListener); } public interface PointHistoryListener { public void pointHistoryUpdated(PointHistory pointHistory); } Called whenever model is updated Updated object (model) View (console, barchart, plotter..) Common interface of all views

31. APointHistoryModel import java.util.Vector; import java.util.Enumeration; public class APointHistoryModel extends APointHistory implements PointHistoryModel { public void addElement (int x, int y) { super.addElement(x, y); notifyListeners(); } Vector listeners = new Vector(); public void addListener (PointHistoryListener pointHistoryListener) { listeners.addElement(pointHistoryListener); } public void removeListener (PointHistoryListener pointHistoryListener) { listeners.removeElement(pointHistoryListener); } void notifyListeners() { Enumeration elements = listeners.elements(); while (elements.hasMoreElements()) ((PointHistoryListener) elements.nextElement()).pointHistoryUpdated(this); } Object evaluating expression (Object on which enclosing method executed) Each write method notifies.

32. Console View import shapes.PointModel; public class APointHistoryConsoleView implements PointHistoryListener { public void pointHistoryUpdated(PointHistory pointHistory) { System.out.println ("**********"); for (int i = 0; i < pointHistory.size(); i++) { PointModel nextPoint = (PointModel) pointHistory.elementAt(i); System.out.println("(" + nextPoint.getX() + "," + nextPoint.getY() + ")"); } System.out.println ("**********"); }

33. Displaying Points View updated whenever any controller changes model

34. Console Controller public class APointHistoryConsoleController implements PointHistoryConsoleController { PointHistory pointHistory ; public APointHistoryConsoleController (PointHistory thePointHistory) { pointHistory = thePointHistory; } public void processCommands() { while (true){ System.out.println("Please enter new point:"); String input = Keyboard.readString(); if (input.equals("quit")) break; int x = Integer.parseInt(input); int y = Keyboard.readInt(); pointHistory.addElement (x,y); } Output method not called directly

35. Console Composer public class APointHistoryConsoleComposer { public static void main (String args[]) { PointHistoryModel pointHistoryModel = new APointHistoryModel(); createConsoleEditor(pointHistoryModel); } public static void createConsoleEditor(PointHistoryModel pointHistoryModel) { createConsoleView(pointHistoryModel); createConsoleController(pointHistoryModel).processCommands(); } public static PointHistoryListener createConsoleView(PointHistoryModel pointHistoryModel) { PointHistoryListener pointHistoryView = new APointHistoryConsoleView (); pointHistoryModel.addListener(pointHistoryView); return pointHistoryView; } public static PointHistoryConsoleController createConsoleController(PointHistory pointHistory) { return new APointHistoryConsoleController(pointHistory); }

36. PointHistoryModel & PointHistoryListener public interface PointHistoryModel extends PointHistory { public void addListener (PointHistoryListener pointHistoryListener); public void removeListener (PointHistoryListener pointHistoryListener); } public interface PointHistoryListener { public void pointHistoryUpdated(PointHistory pointHistory); }

37. Using a More Specific Type public interface PointHistoryModel extends PointHistory { public void addListener (PointHistoryListener pointHistoryListener); public void removeListener (PointHistoryListener pointHistoryListener); } public interface PointHistoryListener { public void pointHistoryUpdated(PointHistoryModel pointHistoryModel); } specific type Allows less polymorphism pointHistoryUpdated does not call addListener or removeListener

38. Using Most General Type Possible public interface PointHistoryModel extends PointHistory { public void addListener (PointHistoryListener pointHistoryListener); public void removeListener (PointHistoryListener pointHistoryListener); } public interface PointHistoryListener { public void pointHistoryUpdated(PointHistory pointHistory); } More general type Allows more polymorphism pointHistoryUpdated does not call addListener or removeListener PointHistoryModel can be assigned