What is code refactoring? The 5 main techniques developers should know.

In the speed of today’s Agile world, code refactoring can sometimes be overlooked. But it is essential to creating and maintaining streamlined code that keeps your programs -and your company- competitive. 

Today, Agile teams are under more and more pressure to write code faster with more functionality in less time. It seems that nearly every programmer has been faced with the task of adding one last function to a project right before its release, but without the time to add it incorrectly and in a way that is organized and lines up with the rest of the codebase. Instead, the function gets added in a sloppy manner, which may technically work, but results in dirty code. 

Sometimes dirty code happens, but this doesn’t mean that you just have to accept it. Instead, implement code refactoring. Code refactoring helps you to create code that is more streamlined and easy to understand. By taking advantage of the different techniques of code refactoring, you can develop cleaner code that works much more efficiently, saving you time, money, and headaches down the road. 

What is Code Refactoring, and What are Its Potential Benefits?

When you ask a developer, “What is code refactoring?”, you may get several answers. Martin Fowler, the software developer who literally wrote the book on refactoring, defines software code refactoring this way: 

noun: a change made to the internal structure of software to make it easier to understand and cheaper to modify without changing its observable behavior

verb: to restructure software by applying a series of refactorings without changing its observable behavior.

When it comes to what is code refactoring, it is the process used by a development team to clean up previously written code without changing that code’s functionality. It is not the process of rewriting code or fixing bugs or improving on observable software aspects, such as the interface.

So, what is code refactoring? In its most basic form, code refactoring makes code more efficient and maintainable. As Ron Jeffries, one of the founders of Extreme Programming software methodology says, refactoring is like clearing a field: Instead of working around the weeds, you clear a path through them.

This has many potential advantages. Dirty code usually results from a developer’s inexperience, shortcuts taken to meet increasingly tight deadlines, poor management of the project, several different developers working on a project over time, or some combination of all of the above. Code refactoring helps to change this dirty code into clean code. With cleaner code, code readability improves, helping the QA and debugging processes to run that much more smoothly, while also improving the maintainability of the source code, in addition to the code’s overall structure and functionality. Code refactoring also helps to make it easier to expand upon the code and add new features in the future. Also, by removing any code duplication or other unnecessary parts, your code will use less memory and perform faster. 

Overall, code refactoring helps to remove and decrease technical debt. Without code refactoring, developers can easily become overwhelmed by technical debt, causing great challenges for any new development, especially when it comes to legacy code.  

All of this combines to cost your team and your organization time and money. The more time that you have to spend interpreting dirty code, the less time you can spend adding new features or improving functionality. Code refactoring helps to improve the more objective attributes of code such as code length, code duplication, and coupling and cohesion, all of which correlate with ease of code maintenance. Code that is easier to maintain takes less time to maintain and often results in a codebase that functions properly. 

Sometimes taking the time to refactor your code may be an unpopular decision in your company. Senior leaders might not only ask, “What is code refactoring?” but they also follow up with, “Why do we need it?” Afterall, the time spent to streamline and maintain your infrastructure is time taken away from newer work. 

But when refactoring is done right, it improves the code that needs to work in order for your program to function and deliver new updates and features that customers want. This helps your company to stay competitive, even after your product is released. 

Code refactoring can also help developers to think about particular design decisions, specifically in the process of collective ownership, when the code may have been written by another programmer. 

Refactoring also helps to reduce the time needed to fix bugs and other errors. If you can specifically and accurately display how much time is spent fixing these mistakes, senior leaders might be more inclined to make time for refactoring.  

When Should You Consider Software Refactoring?

Code refactoring can take place at different times and there are many different approaches. Ideally, though it should be a normal part of your process, not an additional task that needs to be performed. 

That being said, many developers consider the most optimal time for refactoring to be just before updating or adding new features to the existing code. Taking the time to clean up your current body of code before adding in new programming will both help to make your product better, while also making it easier for future programmers to work with your original code. 

You may also want to consider source code refactoring directly after you launch your product. While it may be counterintuitive, this can be a perfect opportunity for teams to perform some refactoring because developers often have more time and availability before moving on to the next company project. 

But there are also many other times to consider refactoring. Before adding a feature is a good time because it can help you to understand other programmer’s code. If you find that someone else has written dirty code, refactor it. This will not only give you clean code, which is much more efficient and easier to use, but those developers who come after you will also thank you. 

Another opportunity for refactoring can be when fixing a bug. Bugs often exist in the dirtiest chunks of code. By using refactoring techniques to clean your code, you’ll find that the bugs may nearly fix themselves. 

A code review is another good time to consider refactoring. This is often the last chance to check for inefficient code before your project reaches the end-user. And happy customers usually buy more of your product, resulting in a happier company to work for.  

Whenever you choose to do refactoring, it’s important to set the groundwork first. Ask yourself and your team a series of questions, including:

  • Which task should be our first priority?  
  • Does the team have the skills needed for refactoring? 
  • Is our team under pressure to ship too quickly?

Other things to consider are the speed of development, any processes in place for dealing with technical debt, as well as any standards in place for documentation. Many of these issues and questions may address the problems which caused the need for refactoring. If you do not explore these different potential challenges, the underlying problems will only continue to grow, regardless of how much refactoring is performed. 

It’s also important to remember that refactoring takes time, so be sure to have all of your codes and processes planned well ahead of time. Also, remember to run tests on your code regularly. Many adjustments and dependencies can become visible while refactoring. Run regular tests to keep your code cleaner and more efficient. 

How to Perform Code Refactoring: The Main Techniques

Now that you know the answer to the question of what is code refactoring, and you know many of its potential benefits, how exactly do you refactor code? There are many different practices for code refactoring, but here are some of the most common.

Regardless of which technique you use, refactoring without safeguards against introducing defects can be dangerous to your codebase. Some safeguards include aids to regression testing, such as automated unit tests, as well as aids to formal reasoning, like type systems.

Read below and find the technique that is best for your company and situation.

  1. Red-Green-Refactor

    What is code refactoring often coincides with unit testing, and one of the most common forms is Test-Driven Development (TDD). TDD is fundamental for Agile methodology.

    Red, Green, Refactor is one of the most popular examples of TDD. Under this method, developers break the refactoring process down into three steps:

    Red: Consider what needs to be developed and write a test without any implementation code. The test will fail.

    Green: Write the implementation code, so that the project passes basic testing.

    Refactor: Find ways to improve the code and implement these improvements, without adding new functionality.

  1. Refactoring by Abstraction

    If you have a large amount of refactoring that needs to take place, refactoring by abstraction may be the technique that you need. This form of code refactoring involves class inheritances, hierarchy, and extraction, with the goal of reducing code duplications.

    One example of abstraction is the Pull-Up/Push-Down method. These are actually two opposing forms of refactoring involving classes. The Pull-Up method moves the classes into a superclass, while the push-down section removes it from the superclass and transfers it down to a subclass.

    Refactoring by abstraction allows you to make big changes to large chunks of code gradually. In this way, you can still release the system regularly, even with the change still in progress.

  1. Composing Method

    Code that is too long is difficult to understand and difficult to implement. The composing method is a code refactoring approach that helps to streamline code and remove any code duplications. This is done through various methods, including extraction and inline techniques.

    Extraction occurs when bits of code are broken down into smaller chunks with the goal of finding and extracting fragmentation. This fragmented code is then moved and replaced with a call to the new method.

    Inline refactoring also helps to create simpler, more streamlined code. It helps to remove unnecessary methods within the code and replaces them with the content of the method.

  1. Simplifying Methods

    As legacy code gets older and older, it tends to become more polluted and complex. In this sense, simplifying methods help to simplify the logic. These methods include adjusting the interaction between different classes, along with adding a new parameter or removing and replacing certain parameters with explicit methods.

    Simplifying can be done in several different manners, such as consolidation of conditional fragments and expressions.

  1. Extract Method

    The extract method is one of the techniques for code refactoring that helps to decrease complexity, while also increasing the overall readability of the code. It involves the moving of a fragment or block of code from its existing method and into a newly created method, which is clearly named in order to explain its function. 

  2. Extract Variable (bonus)

    This method of code refactoring can place an expression that is difficult to comprehend or duplicated throughout your codebase into a separate variable that is more easily understood. This helps to reduce complexity and code duplication. 

Automated Tools are Helpful, But Not Essential

Today, many languages have integrated development environments (IDEs) that can easily automate many of the most common refactoring techniques. These can be extremely helpful for agile teams who need to carry out the refactoring process faster. 

But they are also not essential. Many developers work in languages that do not have tool support. In this instance, the use of frequent testing can be helpful in the early detection of mistakes and errors in the code. 

How Does Sider Scan Support Code Refactoring? 

Sider Scan was developed in order to correct and maintain clean code by detecting code duplication. It is an advanced duplicate code detection tool that quickly scans entire repositories and provides a visual representation of the state of code duplicates. Read more about Sider Scan and its capabilities, and how your code can be refactored.

Aki Asahara

CEO of Sider. Aki joined Fixstars in 2008 and served major clients such as the US Airforce, MIT, USC, Toyota, and Hitachi High-technologies. After his successful tenure, he was appointed CEO of US operations in 2012. He was appointed CEO of Sider in 2019. He holds a Ph.D. in Astrophysics from Kyoto University and is a Certified Scrum Master.

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