308-304B Object-Oriented Design -- Assignment 4\\\ Due date: Tuesday April 16, 2002 before 23:55

308-304B Object-Oriented Design - Assignment 4
Due date: Tuesday April 16, 2002 before 23:55

Practical information

Each team submits only one full solution. Include name(s) and ID(s) in every submitted file. Use the index.html template provided on the assignments page. The other team member (if any) must submit a single index.html file containing coordinates of both team members. This will allow us to put in grades for both team members in WebCT.

Your submission must be in the form of a simple HTML file (index.html) with explicit references to all submitted files as well as inline inclusion of images.

A Class Diagram based on the Observer Pattern customized for our Spreadsheet application as well as comments describing this design.
Python code. You starting point is the solution of assignment 3 on the one hand and the following revision of assignment 1 (to be used as a ConcreteSubject) on the other hand.
Comment your code (link with design) !

You are quite free in your design (and implementation) as long as the following minimum requirements are satisfied:

All GridViews (concrete observers) must reflect the central SpreadsheetData (concrete subject).
The application will start by creating a single SpreadsheetData instance (the concrete subject).
Whenever the user asks to instantiate a new GridView, this is done. At creation time, the GridView constructor gets a reference to the SpreadsheetData passed as an argument.
A GridView will, upon creation, attach itself to the subject. The subject will not only be informed of who is attaching but also of the width and height covered by that particular observer.
Note that when a GridView terminates, it must detach from the subject !
When a cell changes in a GridView, the subject state will be set.
The SpreadsheetData setState() will be responsible for notifying all appropriate observers.
Only those observers observing the changed data will be notified.
A "push" approach will be used: the data will be sent directly to the appropriate observers (who will not have to ask the subject for the state).
(UPDATE) A newly-created GridView must be updated with the contents of the subject (i.e., GridView1 is created and edited. Then GridView2 is created. This new GridView should be consistent with the current state of the subject).