MVC
Reducing software project failures by design pattern(MVC)
Prepared By : Iman Mehmandoust

Contents
• MVC Definition
• MVC Example
• Model
• View
• Controller
• Software Failures
• Why MVC?
• Clarity of design
• Efficient modularity
• Multiple views
• Powerful user interfaces
• Ease of growth
Tuesday, June 9, 2015

Definition
• The Model-View-Controller (MVC) pattern, originally formulated in
the late 1970s
• MVC is an architectural pattern used in software engineering.
• MVC is a software design pattern that separates application logic from
presentation. In this case MVC has a front-end developer and a
back-end developer to work with the same system without
interfering or editing there files by their permeations
• The MVC pattern is most commonly used to create interfaces for
software applications, and, as the name implies, consists of three
elements:(Model View Controller)
Tuesday, June 9, 2015

• The pattern’s title is a collation of its three core parts: Model, View, and
Controller. A visual representation of a complete and correct MVC pattern
looks like the following diagram:
Tuesday, June 9, 2015

Model
• The Model represents your data structures. Typically your model classes will
contain functions that help you retrieve, insert, and update information in your
database.
Tuesday, June 9, 2015

View
• The View is the information that is being presented to a user. A View will
normally be a web page, but in CodeIgniter, a view can also be a page fragment
like a header or footer. It can also be an RSS page, or any other type of "page".
Tuesday, June 9, 2015

Controller
• The Controller serves as an intermediary between the Model, the View, and any
other resources needed to process the HTTP request and generate a web page
Tuesday, June 9, 2015

Example:
A simple way to think of this would be to consider the following:
• A user interacts with the view - by clicking on a link or submitting a form.
• The Controller handles the user input, and transfers the information to the model
• The Model receives the information and updates it's state (adds data to a database or
database interaction, or perform complex calculation for example, calculates todays date)
• The View checks the state of the Model and responds accordingly to the requester or
user (listing the newly entered data, maybe)
• The View waits for another interaction from the user.
Tuesday, June 9, 2015

Software Failures
• Difficult to use the data outside that object.
• Hard to use multiple views of the same data.
• Difficult to synchronize multiple view of the same data.
• Hard to change the UI, when UI and data are locked in the same object.
Tuesday, June 9, 2015

Why MVC?
Just by breaking the program down into the three MVC components, one gains
many advantages. These are the most significant ones I've found through my own
experience:
• Clarity of design:
the public methods in the model stand as an API for all the commands available
to manipulate its data and state. this trait makes the entire program easier to
implement and maintain.
• Efficient modularity:
Changes to one aspect of the program aren't coupled to other aspects,
eliminating many nasty debugging situations. Also, development of the various
components can progress in parallel, once the interface between the components
is clearly defined.
Tuesday, June 9, 2015

• Multiple views:
the application can display the state of the model in a variety of ways, and
create/design them in a scalable, modular way. This comes up in games, with a
cockpit and a radar view, and in my research applications, where I have a view to
display the state of the model and another view that collects data, calculates
statistics, then to saves the data to disk. Both views are using the same data, they
just use the information differently. During the development process, I usually
start out with a text based view, which just prints out the data that the model is
generating. Later, as I create new views, I can use the text based view to verify
the performance of the new views.
• Powerful user interfaces:
using the model's API, the user interface can combine the method calls when
presenting commands to the user. Macros can be seen as a series of "standard"
commands sent to the model, all triggered by a single user action. This allows the
program to present the user with a cleaner, friendlier interface.
Tuesday, June 9, 2015

• Ease of growth:
controllers and views can grow as the model grows; and older versions of the
views and controllers can still be used as long as a common interface is
maintained (the text view just mentioned is an example). For instance, if an
application needs two types of users, regular and administrator, they could use
the same model, but just have different controller and view implementations.
This is related to the similarity with the client/server architecture - where the new
views and servers are analogous to the clients.
Tuesday, June 9, 2015

References
• Definition of MVC:
https://ellislab.com/codeigniter/user-guide/overview/mvc.html
• MVC Advantages:
http://cristobal.baray.com/indiana/projects/mvc2.html
• E-Book
Model-View-Controller: A Design Pattern for Software June 2004
Tuesday, June 9, 2015