Team Code Reading
 

One of the very old practices in the software industry is Code Reviews. The general process is, a senior engineer providing feedback on how a code is written by another engineer. There are many issues we have observed with this approach and we have adopted something called Team Code Reading.

Approach of Team Code Reading

  • Trust: We trust the team members that they have written good code and they are free to check-in their code without someone’s comments. Although this is validated by our functional tests and Unit tests.
  • Team Code reading: We meet as a team to read/go through to each of the lines of code to understand it and try to be critical about it, irrespective of who has written it. The person who wrote the code would normally explain the business and technological background behind it.
  • TODO’s /User Stories: Outcome of code reading is mostly a TODO on the code or a user story on the product backlog.
  • No Finger pointing: Being Critical is fundamental about the code reading session. There are no fingers pointed at the person who wrote it originally. The team takes collective responsibility for the code.

Benefits of code reading:

  • Knowledge Normalization: Since all the team members are part of the code reading session, the product and technology knowledge gets normalized/spread across all the team members. For example, A junior/fresh grad will get lots of technical best practices from the code reading session.
  • Team bonding: Since there is no finger pointing, the team owns the problem in the code, it helps team bond well along with the code.
  • New ideas: Code reading session becomes a platform for brainstorming for new ideas as everyone is in thinking on critically about the product and code. Some innovative ideas come out and have become great product features.

It isn’t all Rosy                                             

There is a cost associated with each of the approaches. Below are the few costs that you have to pay if you are doing Team code reading.

  • The complete team’s time is required to do the team code reading. This is the cost that team members need to spend to get the product/business knowledge.
  • Distraction: There are chances that team gets distracted by some idea/problem. Scrum master or one of team member need to re-align the team towards code, every time there is a distraction.

Concluding remarks

There are always many ways to improve product and code. But the process that is followed drives the effectiveness of the outcome. I believe Team Code reading can greatly help improve the effectiveness of the team.

 

Tail Recursion
 

My Kid’s encounter with Iteration

I was teaching the addition of 2 numbers to my 5-year-old kid. The initial approach is to use fingers in the hand, so she could sum 2 numbers which add up to a maximum of 10. When it went beyond 10, she needed a placeholder (a variable in software terms). Now I taught her to have one of the numbers in mind so that she could just count the fingers for the second number. Again if the second number is bigger than 10, she was limited. When I started questioning about what her next approach will be, I was surprised by her answer. She came up with an iteration algorithm! The Idea is to use a counter (0n paper) for the number of times the set of 10 fingers were counted. This triggered my thoughts about iteration and recursion, hence this blog post.

 Iteration & Recursion

Recursion had been there in software for very long time. Recursion in software is derived from its mathematical formulations. Below are the rules of recursion.

  1. A simple base case (or cases)
  2. A set of rules that reduce all other cases toward the base case

If we can categorize each of the iteration into a form of simple base cases, then the iterative operation can be made recursive. In simple form: A function calls itself. A ‘Recursion’ is a special form of Iteration where no one knows the number of times the iteration will happen. Below is an example of recursion based Fibonacci series generator.

 
        public int Fibonacci(int n)
        {
            if (n == 0)
                return 0;
            else if (n == 1)
                return 1;
            else
                return (Fibonacci(n - 1) + Fibonacci(n - 2));
        }

 

 Stack Based Languages/Frameworks

Recursive logic in stack based languages/frameworks(example .net, Java)are limited by the amount of memory available. This is because these frameworks add the method name and the data(value types) to a top of the call stack for every call to a method. This is done to retain the data in the current method (in the stack) so that when the method returns, the data can be popped out the stack for usage.The data in the stack is not useful if they are not used after the method call.

 
public void PrintCallStack()
{
  var stackTrace = new StackTrace();           // get call stack
  var stackFrames = stackTrace.GetFrames();  // get method calls (frames) 
  foreach (StackFrame stackFrame in stackFrames)
  {
    Console.WriteLine(stackFrame.GetMethod().Name); 
  }
}

 

 Tail recursion (example)

A recursive method is called Tail recursive if the last line of the method calls itself. Since there are no other operations done after the recursive call, the stack data is useless. So the stack need not be built for each of the recursive calls. A compiler is said to be Tail recursive if it can identify the above scenario and replace the caller with called, and the current stack is reused. This is a huge performance optimization and you might never encounter Stack Overflow exception during recursion.

 
public int NonTailRecursiveFactorial(int n)
{
    if (n < 2)
        return 1;
    return n * Factorial(n - 1);
}
 
public int TailRecursiveFactorial(n, a)
 {
    if (n == 0) return a;
    return TailRecursiveFactorial(n - 1, n * a);
  }


Tail recursion is some times equivalent to Goto statements

public int factorial(int n, int a) 
{ 
beginning: 
if (n == 0) return a; 
else 
  { 
     a *= n; 
     n -= 1; 
     goto beginning; 
   } 
}

 

 By the way..

Generally Tail recursion (tail call optimization) is attributed to functional programming languages and unfortunately major programming languages like C# and Java does not support Tail Recursion. But this optimization is available in their sister frameworks F# and Scala. Also there are thoughts like Trampolines and Lambda expressions are far superior method to achieve results than other form of iterative programming. But i think that is a separate post altogether.

Contextual Friendship Framework
 

Recently one of my colleague,  Rahul Rathore and I were on a conversation on object-oriented techniques and we both agree that it has lots of inspiration from the real world. Below is the background of our conversation and what emerged out of that.

Background:

The object-oriented languages like C#, Java are more close to real world. We can mimic the real world behaviors in these languages easily. Scenarios are well captured because of their object-oriented abilities. Inheritance, polymorphism, and encapsulation are principles derived from the real world. In the real world, there are more concepts which are applicable to humans but are not well mimicked in the computer world. One of them is Friendship (between objects).

For better code re-usage, Object-oriented programming languages like C++ have a feature called Friend classes. A class in C++ allows access to all the private & protected members to its friend classes.

But in the real world, we share only a few things with our friends based on the context we are in. We have complete control over what we want to share with our friends and families. This is not the case with C++ friend classes; it shares all the private & protected members to its friends. This poses a threat to the object-oriented theory of encapsulation.

Because of this threat, advanced programming languages like C# and Java have completely removed friendship between objects. But friendship can significantly increase code re-usage and cohesion in objects than breaking them. We wanted to have friendship in C# and Java but still, follow other object-oriented principles.

We observe that C# is very easy to use and highly extendable. So we embraced C# and extended it with the custom module which will enable friendship between classes.

Contextual Friendship Framework:

The framework extends the Microsoft.Net framework to enable friendship among classes. This Friendship framework allows developers to add attributes to classes and its members to enable friendship. There are 2 attributes available.

  1. FriendOf – for classes
  2. AvailableToFriends – for members
  3. FriendOf attribute can be applied to a class whose private and protected members need to be made available to specific friend classes. It takes an array of .Net Types as a parameter. AvailableToFriends attribute can be applied to a class member to allow its access to specific friends only.

A Friend class can access a private/protected member of its friend class by using the ‘MakeFriendlyCall’ extension method exposed by the friendship framework. MakeFriendlyCall method is an extension method that internally uses .Net Reflection to reach to private and protected members. MakeFriendlyCall will allow making calls to private/protected members with AvailableToFriends attribute.

Friendship enables selective sharing of members with friend class based on the class definition. The module provides facility to decorate members of a class for granting access to its friend. Let’s understand this using the below example

 
    [FriendOf(typeof(World))]
    public class Hello
    {
        public string Name { get; private set; }
 
        public void HelloPub()
        {
            Console.WriteLine("Public Hello");
        }
 
        [AvailableToFriends(typeof(World))]
        private string PrivateMethodsAvlToFriends(string name)
        {
            Name = name;
            Console.WriteLine("Private Hello : " + Name);
            return Name;
        }
 
        private void PrivateMethod(string d)
        {
            Console.WriteLine("Private method" + d);
        }
    }
 

    public class World
    {
        private void DoSomething()
        {
            var h = new Hello();
            h.MakeFriendlyCall("PrivateMethodAvlToFriends", "John");
        }
    } 

Here we have 2 classes, Hello and World. The Hello class has two private methods “PrivateMethodsAvlToFriends” and “PrivateMethod”. PrivateMethodsAvlToFriends is decorated with AvailableToFriends attribute. Now the Friend class “World” can make a call to this private method. This can be done by using the ‘MakeFriendlyCall’ extension method exposed generically.

Class Diagram Of the dependencies:

FriendshipFramework

Alternative solutions:

  • Friend class in C++
  • C# has Friend Assemblies which allow all internals of a class visible to another assembly using InternalsVisibleTo attribute. This is more generic than the C++ friend class and does not allow selective access.

Comparison of C++ Friend class Vs Friendship Framework:

Criteria C++ Friend Class Friendship Framework
Security All members are available to friends Granular control over what is available to Friends
Encapsulation Breaks Encapsulation Enhances Encapsulation
Re-Usability Part of the C++ library, so re-usable Fully re-usable as the framework is shipped as a package.
Design Pattern Access Modifier Decorator pattern is used. Also, can be implemented using Access Modifier

Future scope:

We have enabled friendship between classes without breaking encapsulation and security. However, this design can be extended to objects of classes, which makes it closer to the real world. After all, we are not sharing our car with a friend all the times.

Also, the Friendship attributes ‘FriendOf’ and ‘AvailableToFriends’ can be converted to new access modifiers like Public, private, protected. This could be done using Roslyn which is a complier extension to .Net. The Friend framework is available in .Net, but can be implemented to Java framework as well.

 

 

Perspective Designing
 

Recently, I was working with a colleague in refactoring one of our projects. As we added tests, we found few code issues and continued refactoring. Was feeling happy as our unit tests were rearing benefits. However, we know TDD or unit testing does not guarantee clean code. As we progressed, the naming conventions consumed a lot of our time. And eventually, it brought us to a discussion about why specific naming conventions can create a better design. Thought I will share our discussions and practices here.

While we design classes for application, we often think of it as a different subject than ourselves (programmer). When I say different subject, we think of it as a different object and not as a person. When a programmer considers classes/interfaces as personalities and thinks from the perspective of the class, design can change drastically. This is what we call “Perspective designing”. Let’s take an Example:

    public interface ITotalTaxCalculator
    {
        decimal Calculate(IEnumerable products);
    }

    public class TotalTaxCalculator : ITotalTaxCalculator
    {
        public decimal Calculate(IEnumerable products)
        {
            decimal total = 0.0;
            //add total of products etc....
            foreach (var product in products)
        	{
                using(var dbContext = new ProductContext())
                {
                    var productInDb = dbContext.FistOrDefault(prod => prod.Id == product.Id)
                    total += (total * productInDb.taxRate);
                }
        	}
            return total;
        }
    }

In the above example, the name of the class and interface are perfectly fine. But they are impersonal and it’s very hard to think of it as a person and bring in perspective thinking with these names. So we refactored them to ‘ICanCalculateTotalTax’ and  ‘TotalTaxMan’.

public interface ICanCalculateTotalTax
{
    decimal Calculate(IEnumerable products);
}

public class TotalTaxMan : ICanCalculatorTotalTax
{
    public decimal Calculate(IEnumerable products)
    {
        decimal total = 0.0;
        //add total of products etc....
        //blah blah blah..
        total += (total * taxRate);
        return total;
    }
}

These naming conversions have lots of inspiration from in NServiceBus for their class/Interface names. With the new class and interface names, it’s easy to think of them as personalities. However, this does not guarantee good design. So we needed refactoring. Perspective thinking comes in handy especially while we do refactoring When my colleague and I started putting ourselves in the place of each of the classes. We had very reasonable questions which triggered our object-oriented thinking.

Example1:  As ‘ICanCalculateTotalTax’ , why I am having database related behavior?

Example2: As ‘ICanCalculateTax’, why I am having logic to find which language it needs to be presented?

These questions helped us to refactor the code to follow good design principles. When we implement these interfaces/abstract classes, we have clarity on what the class is capable of doing. So we generalized these naming conventions & questioning attitude and derived below two rules to do Perspective designing (think like a class).

  • Give personality to the names of  classes/interfaces (example: ICanCalculateTax)
  • Use the Agile User Stories way of articulating what the class should and should not do. (example: As ‘ICanCalculateTax’, I should be able to provide behavior to calculate tax)

I think, “Perspective designing” can make classes more object-oriented and best practice like SOLID principles automatically fall in line. Let me know your thoughts.

SOLID Principles
 

Many of the old programmers have adopted SOLID principles and it is taught in lots of schools these days. Yet I find many people not clearly understanding SOLID principles. I think these principles are fundamental to creating good object oriented software and every developer should learn them. So I have series of posts for these principles

Single Responsibility : A piece of software always have a single responsibility!
What this basically translates into is that a piece of code should have one and only one functionality. The corollary to this would be that  a piece of code should have only a single reason to change. Some advantages of this would be to ensure minimal change to existing classes in case of a change in requirements, which avoids larger testing efforts for a larger number of classes changed, which cuts down on testing efforts and increase turnaround times, which leads to lower overall cost of ownership for the code, which saves $$.

Take the example of a logging class. As a software developer, chances are pretty high that you’ve all at some point used some form of a logger, be it log4j, its .Net port log4net, Serilog, Elmah or a number of other logging frameworks that are out there. At their core, one thing all these libraries have in common is their focus one one thing. Logging messages. Be it to a flat file, RDBMS, other or other forms of persistence. At no point do these libraries attempt to do anything more than just that. Now a lot of you have also used the same libraries to do something seemingly different, such as  sending out emails for example. The beauty of their design however is that at their core the implementations of these libraries themselves do things at a slightly higher level of abstraction. Namely, they take data, including the message level / severity, to be logged (from a source) and deliver it to a sink (which in most cases happens to be a flat file). While writing to flat files is usually the default implementation of the data sink provided by the frameworks, at their true level of abstraction, they are simply conduits for data, providing solid low level implementations for supporting different logging levels based on configuration. Even the basic things that we take for granted, such as file lock management, rolling log files etc, aren’t truly in the hands of the core framework. These auxiliary features are handled by specific implementations of the log sinks, from DMBS connectors, to file writers, and even SMTP appenders. This brings us to the second principle.

Open-Closed Principle : Software should be open for extension and closed for modification. This weird sounding principle basically attempts to convey that code should be designed such that allows its behavior to be modified without actually modifying the source code for the class itself

Now, historically, this principle has been interpreted in a few different ways, but they have all relied on inheritance to achieve the purported goal.

One interpretation of this principle suggests that a class is ‘open’ for extension if its structure enables us to add new properties or functions in addition to the existing ones provided by the structure. The ‘closed’ part of this interpretation applies when the module by itself is available for other modules for use through its publicly available interface.

The other interpretation of the open closed principle (based on a polymorphic view) refers to the use of abstractions and interfaces to provide and extend certain behaviors, while keeping other (often core) implementation details hidden, and closed to change.

The logger example from the first solid principle is a prime example of this approach, where the implementations of the data sinks (often referred to as appenders) are often supported purely through configuration without touching the core conduit between the source and the sink. The fie appender writing to flat files however, still maintains the Single Responsibility principle by assuming responsibility for only writing to flat files, while also taking care of features and issues specific to flat files such as managing file locks, and often providing out of the box support for rolling log files that prevent log files from becoming too large to manage and view using ordinary text editors.

Liskov’s Substitution Principle : Child class object can be substituted for a base class variable. This one is a slightly more theoretical concept than the others, as unlike the others, it tries more to enforce consistency of behavior between parent and child classes than the syntax of the classes themselves.

The gist of the matter is that if S is a sub type of base type T, then all instances of T in a program should be replaceable with instances of type S without altering the desirable properties of the program. Note the use of the term ‘desirable’, which has a more semantic implication than, say the easier to observe consistency of method signatures that is often associated with overriding / hiding of method implementations in class hierarchies. Without going into the technical details of the precise rules proposed under this rule, it is safe to say that if you see a method or property in a sub type behaving drastically differently from the implementation of its parent, chances are that this principle is being violated in some form.

Interface Segregation: Many interfaces (client specific) is better than the single monolithic interface.

Dependency Inversion : Just depend on abstractions and not implementations.

Learning SOLID principles have changed my programming life and the real one. We shall see each of these principles in more detail in the coming posts.

Language of the Developers
 

There are lots of people who tell me that they need to understand specific design patterns (factory, observer, chain of responsibility etc). And after we spend quite some time discussing the topic they brought up, I ask them why they wanted to understand the original topic. The answers were quite surprising to me. Most of them said, “Design patterns are the trend now”. Some of them said, “I want to write good code”. Some of the candidly accepted “I was asked about this in an interview”.

Well, Design patterns are the new trend in the software industry and are being asked in most of the senior level technical interviews. For me, these reasons don’t qualify to take steps to understand design patterns. But the answer “I want to write good code” was quite interesting. Since a person wants to write good code, he/she is finding ways to improve it by applying patterns. Of course, Design patterns are good to understand and it saves time to know about how to solve a requirement/problem. If we take a step back and see if we really need to understand Design patterns to write good software, the answer is a big NO. Good software’s have emerged even before GoF patterns were documented. So why do we need to understand Design patterns?

When we write the code required to solve the problems, when we write optimal code, when we write code which is readable, testable and maintainable, we would have already applied the correct strategies/principles to solve the problem. But we should realize that when we write code we create a document not only for the compiler but also for other developers to read. How can we explain our code to another developer in a short time? We need a language !! Christopher Alexander (father of design patterns) calls this as the Pattern Language. A language that professional designers can use to communicate designs. He defines what are patterns with respect to this language.

The elements of this language are entities called patterns. Each pattern describes a problem that occurs over and over again in our environment, and then describes the core of the solution to that problem, in such a way that you can use this solution a million times over, without ever doing it the same way twice. — Christopher Alexander

In Software terms, Design patterns are the constructs of a language, professional software developers can use to communicate their design. Until a developer needs to communicate their design/code, they need not know Design patterns! But developers communicate mostly with code. When the code communicates, patterns in the code will help the reader to quickly understand it.

A Developer is an Author
 

When I started this blog, I was skeptical if I can be an author. But what appeared more important to me is spreading knowledge, my thoughts So I continued blogging. After writing few articles what I realize is that writing a blog is not much different from my favorite profession (writing code).

Few similarities between coding and authoring.

  1. Both require deep knowledge of the subject (Domain)
  2. Both require good use of vocabulary
  3. Both require good organizing and formatting
  4. Both require analytic and logical skills
  5. Focus on the reader

If someone is a good writer, he/she can be a good programmer as well. I want to simply put it like this…

Programmer = Author + Technical Knowledge

Most of us(developers/testers)  are focused on attaining higher levels in Technology and unfortunately less in Authoring skills. This is because we think that there is a magical box (called compiler) which will convert our code to machine language and after that, there is no use of our code. This is not true!. When we write code, we are already an author, we are already creating an article/document/story.  And apart from the compiler, there are other readers for your code(Other developers and testers !).  And when they read, they expect to read it like an article. I know this is not a new concept, people like Robert C Martin,  Martin Fowler have spoken/wrote about this long time back. I am just re-emphasizing it from a different perspective.

Let us consider how a small snippet from the novel “A Stone for Danny Fisher” by Harold Robbins.

Harold Robbins

If you observe the paragraphs, each one has a unique purpose. Beautiful short paragraphs doing only one thing at a time (Single Responsibility). This makes it easy for the reader to understand the subject.

Learning: Single Responsibility

Also, observe that the order of paragraphs tells a story. The first paragraph sets the stage for the court, the second one describes the start of the court etc.

Learning: Order the methods in the order, they are being called. Tell the story of your code.

There are lots of quotations in the above snippet. They represent the words of the character. This helps the fast skimmer to skip the unnecessary things and just read the important words.

Learning: Characterize your code, give personality to your classes.

Observe that almost all the sentences are in active voice. They represent the voice of a person. It’s more assertive and stronger.

Learning: Method names should be assertive.

There are lots of similarities between good code and a good novel. We just need to read between the lines to understand them! Besides, each author is different and have their own style of writing and so will be the choices made by developers. These styles will have long-term implications on the success of the project.