Model View Controller With Observer View

Question 1

Basic MVC roles

Answer 1

Model: Hold and manipulate data. Notifies view when changes occur.
View: Takes user input. Presents and visualizes data.
Controller: Receives user input. Converts input messages to the model.

Question 2

How does the observer pattern fit into MVC?

Answer 2

Model becomes observable. View observes model. Controller has listeners that listen to things in the view.

Question 3

View.

Answer 3

Implements observer interface.
update() called by Model

Question 4

Model.

Answer 4

Inherits from Observable class.
Has observer.
addObserver(Observer o)
model.addObserver(view) usually done after model and view are created. Lets the model notify the view with setChanged() and notifyObservers()

Question 5

How can the view be updated?

Answer 5

After notification, the view either pulls data via accessors, or the model pushes data.

Note: If pull used, view must store model as an instance variable.

Question 6

How to push an update?

Answer 6

notifyObservers(Object arg)
Sends an object of our choice to all observers. In this case, the view doesn’t necessarily need access to the model.

Question 7

Controller.

Answer 7

Intercepts events when buttons clicked, and tells model to change.
This indirectly causes observers like the view to be notified.
The view then gets the data one way or another.