14-Jan-2003

1
ModelViewController

• 14-Jan-2003
• Lecture 4

2
Outline

• Previous Business
• Java Help sessions TODAY (GH 227, 5PM 7PM)
• Committee, Year, Person (examples) (docs)
• Thursday 13 office hours for Dimitrova
• Reading Questions
• Lecture Contents
• Relationships Redux
• Model View Controller

3
Reading Questions

• What does relationship fission mean?

Simply separate inheritance relationships from
aggregation


4
Reading Question

• Can composition be other than 1?

No, and this is another difference between
aggregation and composition. Composition
implies 1 on the aggregate side (Node above)
5
Relationship Example

• When multiple aggregates, look for loops

Node
Face

neighbor
6
Relationship Example

• What is difference?

7
Relationship Example

• There are full-time undergraduate students,
  full-time graduate students and part-time
  graduate students

Student
Student
Full-time
Part-time
Ugrad
Grad
PTGrad
FTGrad
Ugrad
PTGrad
FTGrad
8
Relationship Example (cont)

• Courses have a set of students
• Grad courses have grad students

Satisfied??
9
Relationship Example (cont)

• Some grad courses can only have grad students.
  Some ugrad courses can only have undergrad
  students

Satisfied??
10
Model View Controller

• As classes are designed they play different roles
• if not, class has too many responsibilities
• Common responsibilities are
• represent data (or task) as a model
• present state of the model to the user
• enables changes to the model

11
Separation of Concerns

• Model Think REUSE
• represent data (or task) as a model
• ? A Model can have any number of views
• View Think GUI
• present state of the model to the user
• ? is notified of changes and pulls data from
  model
• Controller Think business logic
• enables changes to the model
• ? interchangeable often totally separate from
  M/V

12
Structure of M/V/C

• Simplified Model/View/Controller

Controller
notifies
1
1

Model
View
pulls data
13
Critique of Com/Per/Year example

• What was essentially flawed with the
  Committee/Person/Year example?
• each class is a model but also controller
• elevate relationship to a class
• model checking is a view of the data

Driver
Y
C
Po
ModelChecker
C
Y
Pe
Pe
14
Thursday Assignments

• Review Model/View/Controller
• Read Disciplined Inheritance paper
• a question on the homework will be drawn from
  this paper.
• Review Jan13 and Jan14 code examples
• a question on the homework will come from this
  example
• Exercises
• 2-12
• Review 2.5-2.8

15
References

• Sample Info on Model/View/Controller