Rules are mostly made to be broken and are too often for the lazy to hide behind. – Douglas MacArthur

For the past few weeks, there has been tsunami of debates going on about the principles and rules being followed in the programming world. First initiated by the stackoverflow.com podcast and again triggered by recent CodingHorror post.

Its true that more the rules, more the complexities and constraints. If we just go through the time line of software industry, we can get more and more rules / principles / best practices recommendations as more mature the industry has become or is becoming. The rules and principles of object oriented development that have become popular since early 1990′s or so are the foundation of current software industry trends. But just imagine the beautiful yet complicated world of software development without these doctrines?

Jeff and Joel have been especially critical of Unit Testing and Uncle Bob’s SOLID principles. It is true that there has always been debate among the experts about the magnitude of unit testing your code. While some people may unit test only core components while other may test each and every aspect of their code. Whatever approach people follow, both will be productive and /or counter-productive to some extend. But if we compare the scale of effect between productivity and waste of resources as a result of unit testing, there will be and there has always been in most cases where people have achieved earlier aftermath rather than latter one. I just want to say that yes you can ignore unit test completely and even after that write kickass code but criticizing the concept of unit testing seems to be act of being ignorant especially when you are such a senior programmer. I am also new to unit testing and sometime feel why the fuck I’m writing dual code (original code and unit testing it). But being a rational programmer I will and always follow the industry standard principles and guidelines and I am feeling that my abilty to write clean + resuable code is improving day-by-day.

Jeff and Joel have been especially critical of Unit Testing and Uncle Bob’s SOLID principles. It is true that there has always been debate among the experts about the magnitude of unit testing your code. While some people may unit test only core components while other may test each and every aspect of their code. Whatever approach people follow, both will be productive and /or counter-productive to some extend. But if we compare the scale of effect between productivity and waste of resources as a result of unit testing, there will be and there has always been in most cases where people have achieved earlier aftermath rather than latter one. I just want to say that yes you can ignore unit test completely and even after that write kickass code but criticizing the concept of unit testing seems to be act of being ignorant especially when you are such a senior programmer. I am also new to unit testing and sometime feel why the fuck I’m writing dual code (original code and unit testing it). But being a rational programmer I will and always follow the industry standard principles and guidelines and I am feeling that my abilty to write clean + resuable code is improving day-by-day.
And going to the next topic, I feel criticizing SOLID seems kinda act of irresponsibility. In the world of object computing, SOLID defines the contextual boundary that I take as parameters for making self judgment of my code and measuring myself. For people not familiar with SOLID here is a short intro or you can just google.

• Single Responsibility Principle: A class should have one, and only one, reason to change.
• Open Closed Principle: You should be able to extend a classes behavior, without modifying it.
• Liskov Substitution Principle: Derived classes must be substitutable for their base classes.
• Dependency Inversion Principle: Depend on abstractions, not on concretions.
• Interface Segregation Principle: Make fine grained interfaces that are client specific.

• Release Reuse Equivalency Principle: The granule of reuse is the granule of release.
• Common Closure Principle: Classes that change together are packaged together.
• Common Reuse Principle: Classes that are used together are packaged together.

More information about SOLID can be found here.

Okay for now just forget about Jeff’s post but just look at those comments. After reading some of them I feel the state of dismay at the current state of software industry and came to know there are some people in the world who says GoF Design Patterns is a crap and some just don’t need any rule (kinda cowboy coder).

And the list goes on…

Conclusion

Being a beginner in software world, I may not be appropriate person who could criticize experienced and techies like Jeff and Joel. But sorry guys I don’t give a fuck! I will express my frustration if I’m not satisfied with others’ thought. It’s my right And I also don’t claim that I can follow each and every rules and best practices but still I am trying and will try to write code following them. I want to take programming as the art of craftmanship rather than cowboy work. In my opinion, there are programmers who code to get paid and there are some who code not only to get paid but also as a chance to learn and improve continuously. So, what type of programmer are you?

Yes you can write kickass code by not following any rules or just by creating your own rule but the question is how are you going to compare the quality of your code without these principles and rules?

Readers what do you think?

The title of this post has been taken from this tweet.

In my previous post, I had posted a link about the interview with the design patterns guru Erich Gamma. After reading that article, I came to know about the concept of public and published method in a component, class or interface.

“Something can be public but that does not mean you have published it.” – Martin Fowler

For past few days, I have been trying to justify this statement. In the process, I did google the term, but I was unable to find any interesting post until I found the white paper written by Martin Fowler himself (I am damn lucky ). The white paper and two answers I got in the stackoverflow about my question regarding public and published concept has helped me a lot to understand and difference between these almost identical terms.

The scenario of public and published arises especially in the distributed environment when one has to publish his/her code in the form of API to other developers. Once the method or interface or class is published, changing it later will certainly break other’s code.

In JAVA and .NET, with release of new version number of methods, class or interface are treated as deprecated. Changing the behavior of those legacy modules means breaking the code being dependent on them. So, attributes like deprecated are used to inform the clients or service caller to updated their code. APIs are not defined by their source rather by contracts usually in the form of documentation or with the use of refactoring tools and sometimes with the help of reverse engineering with the use of Reflection (System.Reflection in .NET)

Here are the list of advices given by Fowler on publishing interfaces:

• Don’t treat interfaces as published unless they are
• Don’t publish interfaces inside a team (this one related to code ownership)
• Publish as little as you can as late as you can
• Try to make your changes additions

My Implementation

Lets suppose, Boeing‘s Dreamliner uses engine made by Rolls Royce (in reality it does use). For efficient use, there must be a contract between Boeing which call and invoke APIs and services and Rolls Royce which is responsible for designing the contract.

In this scenario, Rolls Royce’s services invoked by Boeing should be according to the contract and the interfaces provided within that contract are all published.

If the contract provides only one interface i.e. IRollsRoyceEngine as published and while other interface as public but not published then, Rolls Royce should be responsible for the change in the IRollsRoyceEngine interface only not IRollsRoyceEngineAnalyzer.

Boeing can of course use IRollsRoyceEngineAnalyzer but Roll Royce is not bind to inform the change in the interface if it happen in the future.

Conclusion

Differentiating published and public interface while designing the contract and API can be encouraging thing to do in the context that change will happen and it is inevitable and it’s just the matter of time. Updating an interface should not break the legacy interface.

Hmm…quite easy to say but certainly not so easy to implement in real projects. Now I am really eager to implement the concept of published and public interfaces and see what it is truly worth of!

Model-view-controller (MVC) is both a design pattern and an architectural pattern used in software engineering. – Wikipedia

Historical Background

MVC was started by Ward Cunningham and Kent Beck who were working with SmallTalk and designing GUIs at Xerox PARC. The original implementation is described in depth in the influential paper Applications Programming in Smalltalk-80: How to use Model-View-Controller.

What is Pattern?

A pattern is a solution to a problem in a given context. Christopher Alexander says each pattern is a three-part rule which expresses a relation between a certain context, a problem, and a solution. Pattern in the software development was especially popularized from the publication of the book named Design Patterns: Elements of Reusable Object-Oriented Software by Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides or often referred to as Gang of Four (GoF). Design patterns represents a solutions to problems that arise when developing software within a particular context.

What is MVC?

MVC can be defined as an architectural pattern that is used while developing interactive application on the web. As the name suggests there are three major components of MVC:

• Model: Encapsulates core data and logic. Model is often related with the business logic of the application. It knows all the data that needs to be displayed. It is always isolated from the User Interface (UI) and the way data needs to be displayed.
• View: It is the UI part of the application. It uses read-only methods of the model and queries data to display them to the end users. It may be a window GUI or a HTML page. View encapsulates the presentation of the data, there can be many views of the common data
• Controller: It acts as a interacting glue between models and views. It accepts input from the user and makes request from the model for the data to produce a new view.

How it works?

Advantages

• Separation of Concern: Since MVC has three components whose operations are quite isolated from each other. For example; people working on view part can concentrate only on the UI and the part visible to the end users; people working on model part can concentrate on the business logic and the functional requirements of the system or ‘What’ part of the system and finally people working on the controller section may have knowledge of both view and model section so that interaction between other two components could be made easily. There is clear designation of roles for each stakeholder of a system.
• Modularized Development: Modularization is the process of dividing any complex problem into smaller sub-modules and we human have been following this approach from the time unknown. In MVC, we divide our system into three parts in order to reduce complexity.
• Pattern based development: As defined in the earlier section, pattern is the proven solution for any problem in a particular context. MVC itself is a pattern implemented in the presentation layer where it handles user’s interaction (controller) with a particular model through view. MVC is a proven solution for many contexts especially interactive web applications so following it in order to build a system may be comparatively more effective and trust worthy.
• More Control over URLs: Almost all MVC based frameworks have the feature of URL routing that gives us more control over the URL we desire. For example; http://www.foo.com/prajwal/edit where ‘prajwal’ may be unique ID and ‘edit’ may be controller action.
• Maintainability and Code Reuse: The Modular design of MVC supports the design goal of reusable software. As MVC requires a definite rule and style for coding, the result can be much more maintainable and reusable software.
• Test Driven Development: By following MVC, one can easily tests each and every part of the system. Moreover, most of the MVC frameworks do have one or more built-in testing frameworks.
• Platform and language independent: MVC is simply a pattern which can be implemented in any language or any platforms. Most of the popular languages and platforms like Java, .NET, PHP, Ruby, Python have one or more MVC based frameworks. So you once you know the MVC funda, you can implement in the platform of your choice.

Disadvantages

• Adds additional level of complexity: MVC can increase the level of complexity of a system since. MVC requires in depth planning so, any wrong decision taken early could impact the whole application life cycle.
• More files to manage means more headache: This may be context dependent. Some people might feel odd when dealing withe more files. A MVC based system has comparatively more number of files than a non-MVC based system.
• Rigorous separation between the model and view can sometimes make debugging more difficult: In my experience, debugging a MVC application is still quite difficult as compared to a non-MVC application. I am talking about my experience while working with CodeIgniter, a PHP based MVC framework. But the same is not true when talking about ASP.NET MVC.

Implementations of MVC as web-based frameworks

.NET

• ASP.NET MVC Framework
• Maverick.NET
• Monorail An ActionPack inspired MVC framework from the Castle Project
• ProMesh.NET Open source MVC Web Application Framework for .NET 2.0 or higher

PHP

• CodeIgniter
• Cake PHP
• Akelos PHP Framework
• Symphony
• Zend Framework

Python

• Django
• Pylons
• TurboGears for Python
• web2py Web Framework

Ruby

• Ruby on Rails
• Nitro
• Merb
• Camping

Java

• Cocoon
• Grails
• Spring MVC Framework
• Apache Struts
• WebObjects
• JSF

Conclusion

As the benefits of MVC out number the disadvantages, in my opinion one should follow this approach when creating interactive web applications with high degree of agility.

In software engineering, an abstract type is a type in a nominative type system which is declared by the programmer, and which has the property that it contains no members which are also not members of some declared subtype.
Interface generally refers to an abstraction that an entity provides of itself to the outside. This separates the methods of external communication from internal operation, and allows it to be internally modified without affecting the way outside entities interact with it, as well as provide multiple abstractions of itself. It may also provide a means of translation between entities which do not speak the same language, such as between a human and a computer. Because interfaces are a form of indirection, some additional overhead is incurred versus direct communication. -Wikipedia

In Java, .NET and PHP 5 there are three ways to create and object i.e. inheritance, composition and interface.

• Inheritance defines “is-a” relationship. Example: Student and Programmer is a Person
• Composition defines “has-a” relationship. Example: Class Student contains class Book
• Interface only models the behavior of an object. Example: Student and Programmer are both Nameable and both may have actions.

In Java, .NET and PHP 5, multiple inheritance (child class with more than one parent class) is not allowed so, interface can be used as a powerful tool to separate implementation. Interface is not a strict “is a” relationship. Abstract class represents some sort of implementation and it is a strict “is a” relationship. For example: A dog is a mammal and a reptile is not a mammal showing strict relationship whereas both dog and reptile may be nameable and both may have some actions.

As we know that interface and abstract class both provide abstract methods so, making the best use of them is crucial in the object oriented paradigm. Abstract class provides both concrete and abstract methods whereas interface provides only abstract methods. Lets go through an example:

Assume that we have an abstract class Person and its concrete implementation class Student and Programmer. We have an interface called IWork that may or may not be implemented by the concrete classes Student and Programmer. We also have a composite class Address, though it is not required while distinguishing between interface and abstract class, using composite class will help us to clarify the scenario.

Class Diagram

Abstract Interface Class Diagram

C# Code

Abstract Class - Person

Interface - IWork

Class - Address

Class - Programmer

Class - Program

Conclusion

• Classes in a strict inheritance relationship must be related.
• Interfaces can be used for classes that are not related. In the above example, only Programmer class is implemented but it is not necessary that Student also implements the IWork interface.
• An interface never provides any implementation, only behavior.

References

• http://en.wikipedia.org/wiki/Interface_(computer_science)
• http://en.wikipedia.org/wiki/Abstract_type
• The Object-Oriented Thought Process (3rd Edition) (Developer’s Library) by Matt Weisfeld

You can download the example from here.

I am going through the book named “The Object-Oriented Thought Process (3rd Edition) (Developer’s Library) by Matt Weisfeld”. I got some interesting facts in the chapter 9 “Creating Objects” of this book which I want to share. Being a software developer, we know that we always want to create a stable system. The 1962 article titled “The Architecture of Complexity” by Nobel Prize winner Herbert Simon noted some quite interesting characteristics of the stable systems:

• Stable systems have hierarchy. Each system is built from a sub-system and each sub-system is still built from another sub-system forming basis for functional decomposition. This approach has been used in structural approach also.
• Stable system is nearly decomposable.
• Stable system evolves from the the simple sub-system that have worked.
• Stable systems are always composed of only few different kinds of sub-systems

Another fact I want to share is about the design decision that is required to be made. We know that a system needs to be loosely coupled and highly cohesive. But what should we do for achieving this? Three points have been proposed by the author:

• Which objects collaborate with each other?
• How many objects participate in each collaboration? (This represents cardinality)
• Is the relationship mandatory or optional?

I really recommend this book to any developer who wants to enhance his/her knowledge about the object oriented development.