Model-View-Controller (MVC) is probably the most used architectural solution for User Interface design and web programming; First defined at the end of the 70s, MVC has been progressively adapted and morphed into a wide range of subtypes and variations, so much that the plain term "MVC" without additional qualifications has lost specificity. As a general interpretation, it is a rather loose guideline for organizing your code when the data and visualization parts of your application need to interact while staying as loosely coupled as possible. How this is accomplished in practice depends on the particular MVC incarnation.

MVC is implemented through an aggregation of more fundamental design patterns such as Composite, Mediator and Observer/Notifier. The complexity and variation in style of MVC arises from all the possible uses and variations of these independent patterns to satisfy the potentially elaborate requirements of a GUI.

The objective of this book is to explore variations and nuances of MVC, comparing and analyzing them. I will talk about "MVC" generically to refer to all its different incarnations, and with a more specific name to refer to specific ones. The common point of all variations is to decide “who is responsible for what” and “who knows about whom” in the interaction between User and Application data. Different MVC variations assign responsibilities in a different way, connect or organize protagonists in a different way, or add intermediate objects to gain more flexibility and satisfy peculiar use cases.

This book is structured as follows:

• The first chapter will start from the simplest form of GUI with state: the Smart-UI. We will then progressively refactor Smart-UI into a “Traditional MVC”, followed by a definition of its components, roles, and communication patterns.

• Once equipped with nomenclature, the second chapter will introduce variations of Traditional MVC to address specific constraints and practical needs.

• The third chapter will expand the concept of MVC to hierarchical MVC schemes.

• In the fourth chapter we will focus on special collateral techniques that may emerge from a complex modern GUI.

• In the fifth and final chapter, we will specifically focus on Web MVC and its implementations.

Throughout the book, some example code in Python will be used to clarify design ideas. GUI rendering will make use of the excellent Qt toolkit, through PyQt4. Qt provides pre-made mechanisms to address most of our needs, but in the upcoming code these mechanisms will occasionally be skipped on purpose to demonstrate a more general approach.

I started writing this book as an accident. Initially, I wanted to write a series of blog posts to describe Model View Controller and a few related patterns. As I gathered more and more information from the net and my personal experience, I suddenly found out that the amount and structure of what I wrote was beyond the scope of a blog, hence the decision to re-label it as a book. I am happy with the decision, because it gave me freedom to add material I would not have added otherwise.

This works presents and enriches design solutions, best practices, and experiments made available by countless blog posts and comments. To these authors goes my acknowledgement and gratitude. Being a work in progress, there's still a lot to be done. Please be patient, but feel free to send me feedback, pull requests, and take advantage of the material already present.

This book is released under GFDL license, and free (gratis), mainly for three reasons

• As stated, most of the material here presented was gathered from the net. It was my personal effort to organize this knowledge, but I had a lower startup barrier.

• I already published a book with a commercial publisher, and from my experience and math, I think that if I put a book on the web and accept donations I would probably get more money and feedback than going through a publisher.

• This book is part of my portfolio as a professional in software development and design, and I am proud to focus on a personal project to increase my competences.

That said, I gladly accept donations:

• on GratiPay
• on bitcoin
• on PayPal (using my email address stefano.borini at ferrara dot linux dot it)

The sources of this book are available as a github repository at the following URL:

https://github.com/stefanoborini/modelviewcontroller-src

I also have a personal website at http://forthescience.org where you can find more information about me, my curriculum and activities.