1. Model-View Controller
Design pattern presentation and discussion
Rajat arya
EFECS * OIM
DAWG MVC Presentation

2. Agenda Definition History / Origins Functional Description
what is this fancy thing called MVC?
History / Origins
where does it come from?
Functional Description
how does MVC actually work?
Goal / Benefits
why is it important?
Example Scenarios
where could MVC be used?
Sample MVC Implementation Review
lets see this thing actually working
Modern Implementations
where does it exist right now?
Questions?
Reference Materials
DAWG MVC Presentation

3. MVC Definition
The Model-View Controller Paradigm is a triad of classes used to build modular applications. MVC consists of three components (objects): Model – application object (data) View – user interface (presentation) Controller – defines how user interface reacts to user action
DAWG MVC Presentation

4. History First Appeared Formally in:
“A cookbook for using the model-view controller user interface paradigm in Smalltalk-8”
by Glenn E. Krasner and Stephen T. Pope
Journal of Object-Oriented Programming, 1(3):26-49
August/September 1988
DAWG MVC Presentation

5. Functional Description Intro – Observer Pattern
MVC utilizes two applications of the Observer Pattern
Observer Pattern (aka Publish-Subscribe)
Attach / Detach / Notify
Decouples Subjects from Observers, subjects do not know about observers directly
Observer Docs:
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6. MVC Functional Description
MVC Definition: Specific application of the Observer Design Pattern
Model is application object (data)
View is the user interface (presentation) – observes Model
Controller defines way user interface reacts to input – observes View
Observer Pattern Used Twice (Controller observes View and View observes Model)
View
Controller
Model
DAWG MVC Presentation

7. MVC Functional Description (2)
Controller maintains knowledge of both View and Model, View has knowledge of Model
Controller observes changes in View (1), informs Model (2)
View observes changes in Model (3) and updates
View
(1)
Controller
(3)
(2)
Model
DAWG MVC Presentation

8. Goal / Benefits Modularity Flexibility Maintainability Testability
decoupling components
allows each component to be versioned independently
worked on by individuals on team (UI person, DB person, etc)
Flexibility
multiple Views for one Model (web frontend, desktop frontend, mobile frontend, etc)
replace one component (replace data storage from flat file to database)
Maintainability
only change one component where bug exists, less risk in late changes
Testability
each component communicates through contract so each component can be unit-tested independently
DAWG MVC Presentation

9. Example Scenarios Spreadsheet application (classic)
same data (model) spreadsheet can have multiple charts (views)
updating spreadsheet should result in updated charts
example of multiple views, single controller, single model
Scaling an application
view is desktop or web, model is a flat-file database
updating the database to clustered set of SQL servers
only model needs to take changes for architecture, controller connects to new model and doesn’t know that the model is now backed by several DBs instead of one file
Multiple user interfaces to application
web interface, mobile phone interface, point-of-sale interface, desktop interface
multiple views, multiple controllers, single model
DAWG MVC Presentation

10. Sample Implementation Review
Small WPF Application written in C# to illustrate how MVC. me if you would like a copy of the source code.
DAWG MVC Presentation

11. Modern Implementations
GUI Frameworks for desktop applications
Application Kit – part of Cocoa for OS X desktop apps
GTK+ - part of GTK libraries, used in lots of apps
Microsoft Foundation Classes (MFC) – Document/View Architecture
Java Swing
Windows Presentation Framework (WPF)
TK Toolkit – part of Tcl/Tk
Implementations of MVC in web-based frameworks
ASP .NET MVC Framework (.NET)
ProMesh.NET (.NET)
Grails (Java)
Struts (Java)
Spring (Java)
PureMVC (JavaScript)
Ruby on Rails (Ruby)
Zend Framework (PHP)
Django (Python)
Pylons (Python)
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12. Fin.
Questions?
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13. Reference Links
Design Patterns: Elements of Reusable Object-Oriented Software
If you get nothing else from this talk, please go look this up – it is the most important book I’ve read regarding object-oriented programming:
MVC
Observer Pattern
DAWG MVC Presentation