The advantages of clean code are undeniable: better readability, easier maintenance, faster development and satisfied developers. But the crucial question is how to achieve clean code when your daily work is dominated by tight deadlines, complex requirements and constantly changing teams. How do you avoid your code becoming a confusing, incomprehensible construct?
In this comprehensive guide, we show you how you can write clean code and maintain it over the long term despite all the challenges. Discover the clean code principles and practices that will tidy up your code and improve your software development processes for the long term – for projects that are successful not only today, but also tomorrow.
Clean Code – An Overview
In a nutshell, clean coding is a programming practice that involves writing code in a way that makes it easy to read, understand and maintain.
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The principles of clean code include the following parameters:
- Specifications are met: The code must meet the functional and technical requirements.
- Readability and expressiveness: The code should be written in a clear and understandable way.
- No surprises: The code only does what it is supposed to do, without unexpected side effects.
- Easily modifiable: The code is easy to adapt and extend.
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The values of clean code are:
- changeability
- efficiency and
- continuous improvement.
These values help to design valuable software that solves real customer problems.
Clean code – the advantages
In addition to improved readability, comprehensibility and maintainability through clean code principles, clean code offers many other advantages:
Quick adaptability & efficient maintenance
Clean code significantly reduces the time to value. However, ignoring it can lead to a complete standstill in development in the long term.
Comprehensibility and good testability
Clean code ensures stable software with fewer errors caused by misunderstandings. In addition, well-tested code is more likely to better meet stakeholder requirements.
Less onboarding time
New developers can find their way around the code more quickly, which reduces training time and reduces dependence on a select few experts.
Simple replacement process
At the end of its life cycle, the code can be replaced more easily because tasks and side effects are clearly identifiable, which reduces the potential for errors.
Increased developer satisfaction
Clean code improves the quality of work and increases developer satisfaction, while messy code often causes frustration.
Clean code focuses on what matters: delivering value. It ensures fast, error-free and smooth development, while poor code constantly creates unexpected obstacles and destroys predictability. Clean code is therefore not just aesthetic, it enables teams to function in the first place.
Clean code development – a closer look
The term ‘clean code’ was coined by Robert Cecil Martin in his book Clean Code: A Handbook of Agile Software Craftsmanship. This work inspired many other projects. But what exactly is clean code?
The everyday work of a developer involves, among other things...
- implementing new features,
- reviewing colleagues' code and
- fixing bugs.
To do this, the relevant piece of code must not only be found, but also understood – a real challenge if the code was written by another developer or has not been touched for a long time. This is exactly where clean code comes into play: clean code should be easy to change and easy to read, thus making the daily work of developers easier.
KISS, DRY, SRP – Clean code principles at a glance
Clean code principles are guidelines that, when followed, can lead to clean, efficient, and maintainable code. The key word here is ‘can.’ It is important to understand that these principles serve as guidelines and that strict adherence does not automatically result in better code. As with many aspects of software development, the principle ‘it depends’ applies here as well.
At the end of the day, the developer must decide for themselves which principles work for them and which path they want to take. Pre-defined principles are no substitute for a good developer. The whole thing is a bit like a recipe book: it helps, but the cook still needs to know what they are doing.
Preferred readability
‘Put yourself in my shoes!’ This request is particularly important in programming, as no programmer works in a vacuum. Therefore, the following principle applies: If there are several ways to do something, choose the one that is easiest for the reader to understand.
This principle is particularly important when naming variables. Don't just call your variables ‘ints’; choose meaningful names such as ‘ElapsedTimeInMilis’. This increases clarity, facilitates understanding and significantly improves the maintainability of your code.
Keep It Simple, Stupid (KISS)
To implement this principle in the best possible way, it is best to follow some tried-and-tested advice: explain it as if you were explaining it to a five-year-old.
The idea behind the KISS principle is that code should be as simple and clear as possible. It is not about showing how clever you are, but about ensuring that others can understand the code. So always ask yourself: Is this really the simplest solution? Could I explain it to a five-year-old?
This approach avoids unnecessary complexity and creates lean, easy-to-understand code. So focus on the essentials without getting lost in details. This makes maintenance easier for everyone.
Don't Repeat Yourself (DRY)
Let's move on to the KISS principle. Have we already explained this? Oops! This shouldn't happen when coding. Duplication must be avoided at all costs so that you don't have to rewrite the same code over and over again. This saves development time and means that errors only have to be fixed once.
Good to know: DRY (Don't Repeat Yourself) always requires careful consideration on the part of the developer. Two pieces of code that look the same are not necessarily duplicates if they can develop differently.
Single Responsibility Principle (SRP)
This principle is easy to explain: Each unit of code should have exactly one clearly defined task. This increases readability and simplifies testing.
Here is an example to illustrate this principle: Imagine a class that is responsible for both managing orders and printing invoices. According to the single responsibility principle, this class should be split into two separate classes:
- Order – manages orders.
- Invoice printer – prints invoices.
This means that each class really only has a single task. This makes the code clearer and easier to maintain.
Single Level of Abstraction (SLA)
Another principle of clean code is the ‘single level of abstraction’ principle. It states that the content of a function should always be at a single level of abstraction.
To illustrate this, let's imagine that the driver of a car is replaced by the function ‘DriveTo’. This function now controls the car – including the brakes, accelerator and steering wheel. However, it should not deal with more complex processes such as fuel supply and ignition. According to the SLA principle, these tasks belong to a different level of abstraction. This makes the code easier to read and understand.
Good to know: A reference to different abstraction levels can be the grouping of lines of code by comments or blank lines. These visual blocks often indicate that the operations belong to a separate abstraction level. Outsourcing these blocks to separate functions can improve the readability and structure of the code.
Composition on inheritance
Inheritance means creating classes that take on the properties and methods of other classes. Inheritance has valid uses, but if used incorrectly, it can lead to very messy code.
The problem is that abstraction via inheritance links classes and their properties very strongly. This construct then becomes difficult to test and, in the worst case, details of the child classes even affect the parent classes, making the code difficult to change.
The solution to this is composition, which prevents this problem. Instead of linking classes, they remain independent of each other. They only work together via clearly defined interfaces. This keeps the code cleaner, easier to test and easier to change.
Good to know...
One indication of poor code is when a parent class makes decisions based on the type or a property of the child class.
Be consistent
It doesn't help anyone if you adhere to all other principles but then choose a different approach in every section of code. This means that you should treat as many aspects as possible in a consistent manner!
This applies to the language used in the code, code conventions and also solution patterns for recurring problems. Consistency in code increases comprehensibility and reduces the training time for new developers.
Proven practices for clean coding
In addition to clean code principles, there are also best practices that help developers write clean code. Here are some of the most important methods:
Boy Scout Rule
This practice can be summed up perfectly with the words ‘Always leave the code a bit better than you found it’.
Similar to scouts who leave a place cleaner than they found it, developers should always make the code a little better than they found it. This practice helps to implement clean code step by step and without much additional effort.
Root cause analysis
Treating symptoms superficially is like painting over cracks in a wall – it looks good, but doesn't last long. In the long run, it even leads to increased complexity and error-prone code. Developers who follow clean code principles should therefore always look for the root cause of the problem and fix it.
Iteration, reflection & the dual control principle
Clean coding is a process that requires regular monitoring and improvement. It is therefore important to reflect on the code you have written at an early stage. This can be done, for example, by applying the dual control principle – either through code reviews or pair programming. This not only provides early feedback on implementation, but also contributes significantly to the cleanliness of the code.
Regular formats, such as a tech weekly, where clean code can also be discussed, contribute to the further dissemination of knowledge and the improvement of the code. On a larger scale, a dedicated, feature-free sprint for code quality is also conceivable. In this sprint, the added value created is not a new feature, but instead better quality and preparations for sustainable product development.
Test Driven Development (TDD)
Test-driven development (TDD) is another method that can help promote clean code. TDD is a design strategy for code that uses tests to guide the development of the implementation and enable safe refactoring.
TDD encourages you to design the interface of the components first, as this is what the first user, namely the test, needs. This results in clearer and simpler interfaces and strongly focuses on technical correctness, documentation, loose coupling, high cohesion and thus on clean code.
Refactoring is an important methodology in clean coding. It helps to clean up and improve messy code without compromising existing functionality.
Dealing with technical debt
Once awareness of clean code has been established, you need to consider how to deal with unclean code. Often, there is no time for improvements at the beginning.
In such cases, it has proven helpful to treat unclean code as technical debt and manage it in a technical debt backlog. This ensures that identified problem areas are not forgotten and that improvements can be planned. Consciously planning regular reviews and improvements, both through dedicated time slots and as part of regular development work, creates the necessary framework for this.
Get the most out of your software development process with clean code!
Clean code development – challenges during implementation
At this point, we would of course like to say that implementing clean code only brings advantages and no challenges whatsoever. A real walk in the park – relaxing and without any risk. But that would be a lie, because no major change is ever without challenges – and clean coding is no exception.
However, every challenge can be overcome. Let's take a look at the potential challenges you may face during implementation.
Customer focus and technical debt
Some of the biggest challenges of clean code lie not in the code itself, but in the priorities. If the focus is too much on new features and clean code is neglected, this leads to increasing technical debt and a decrease in development speed.
This problem can be counteracted by returning to the tried-and-tested practices of clean code. In particular, using a backlog for technical debt can lead to improved code and priorities.
Unclear requirements
Another challenge in implementing clean code can be unclear requirements. With unclear requirements, there is a risk that the complexity of the solution will not match the problem. It may either be unnecessarily complex or fail to cover all cases.
The naming and use of domain terms in the code can also be incorrect if the requirements are unclear. This jeopardises the correctness of the solution – it may fit the requirements that have been developed, but not the actual goal.
To counteract these problems, the following solutions should be considered:
- Clear requirement definition: You should ensure that the requirements are clearly defined in order to make the solution complexity appropriate.
- Correct naming: Pay attention to the careful naming and use of domain terms in the code, even if the requirements are unclear.
Internal challenges and discipline
One of the biggest challenges of clean coding is that the process is never really complete and therefore requires continuous discipline from everyone involved.
It becomes particularly difficult when these principles are introduced retrospectively in a company. In such cases, a deep understanding of the existing software and the technical domain is essential. However, even experienced developers occasionally produce unclean code, which makes understanding even more difficult and the entire conversion process significantly more complex.
Clean Code – tidy up your code
At MaibornWolff, clean code is more than just a buzzword – it is the core of our work. Whether in development projects, software audits or training courses, we focus on the highest code quality and pass this knowledge on to our customers. Together with your team, we ensure that you get the most out of clean code. We tailor our support flexibly to your needs. Clean code is our standard – for sustainable software that delivers.
FAQs on clean code
What is clean code?
Clean code refers to code that is easy to read, understand and maintain. It is free of unnecessary complexity and fulfills all functional requirements without surprises.
What clean code principles are there?
Important principles include KISS (Keep It Simple, Stupid), DRY (Don't Repeat Yourself), the Single Responsibility Principle and the preference for composition over inheritance.
How does clean code relate to agile development?
Clean code supports agile methods through short feedback cycles and the ability to react quickly to changes, which leads to more efficient development.
How is refactoring related to clean code?
Refactoring is the process of improving existing code without changing its functionality. It helps to turn unclean code into clean code by optimizing the structure and increasing readability and maintainability. Refactoring is a continuous process that implements the principles of clean code in existing projects.
Richard Gross is Head of Software Archaeology and has been working in IT modernisation since 2013. As a member of the division management team, he drives forward topics such as technical excellence. As a team leader and architect, he supports teams in achieving a return on investment as early and continuously as possible. To achieve this, he coaches teams in code quality, test automation and collective ownership. His technical focus is on hexagonal architectures, test DSLs, hypermedia APIs and the expressive and unambiguous modelling of the domain as code. Richard shares his knowledge through active pair programming, training courses, technical articles and presentations at international conferences. He has also been involved for many years in the open source project CodeCharta, which enables non-developers to gain an understanding of the quality of their software.