Refactoring – the key to clean code

Refactoring brings order to code chaos, improves code quality, and enables your team to work efficiently without encountering unexpected problems. Learn everything you need to know about code refactoring in this guide! Discover how to turn a chaotic warehouse into a perfectly organized storehouse.

When refactoring code, the existing code is restructured in many small steps, known as refactorings, without changing its basic functionality. The aim is to increase the comprehensibility of the code and thus enable resource-saving further development in the long term.

In practice, this means that the code is tidied up and the software quality is improved without the users of the system noticing any changes in functionality. This includes, for example:

• renaming variables,
• introducing new abstractions,
• reducing nesting depth and
• removing unused code.

The aim is to model the technical and domain language as clearly as possible so that teams always remain capable of acting and can integrate new functions.

Code that isn't maintained over a long period of time can become more and more chaotic. In this case, the code quality deteriorates significantly, understanding disappears and complexity increases.

At this point, at the latest, complaints about so-called ‘spaghetti code’ start to pile up. And for good reason! This causes a significant increase in implementation effort, makes troubleshooting more difficult and prevents efficient work. In short: it leads to increasing paralysis.

Whether for debugging, implementing new features or during a review, refactoring should be considered at every stage of software development. This is because it offers a number of advantages that improve the software:

• Reduced complexity and comprehensibility: The complexity of the code is reduced, making it easier to understand. This facilitates teamwork and simplifies maintenance.
• Testability: A clearer structure ensures better testability and helps to identify errors at an early stage.
• Debugging: Bugs can be found and fixed more quickly because the code is clearer.
• Resource conservation: An optimised code base reduces resource consumption and increases efficiency.

And the best thing about it: Refactoring can be done during ongoing development without interrupting the development process.

• Rename: Rename variables, methods or classes to make them more meaningful and understandable.
• Embed: Move compact and understandable code directly to the location where it is needed, rather than outsourcing it to methods or variables.
• Extract methods: Move complex and confusing code segments into separate methods and describe them with meaningful method names.
• Move to local variables: Instead of leaving values without context in the code, it makes sense to store them in descriptive variables. For example, 3.14 should be referred to as PI.
• Add parameters: If data changes frequently within a method, it should be passed as a parameter. This extends the parameter list and reduces the need to modify the method.
• Move to field: Move recurring values in a class to a common field to simplify maintenance.

These methods should be selected and applied as needed and according to project requirements.

There is no single approach that is suitable for every project. Each project requires individual measures to be defined: what needs to be restructured, how, and to what extent. Since there is no one-size-fits-all solution, this is only a rough guide.

At MaibornWolff, however, we place great value on transparency and knowledge transfer: That is why we accompany you from the very beginning on your way to a maintenance-friendly, resource-saving and future-proof application. With our decades of experience in software development and in performing our software health checks, we tailor the following approach to your individual needs – whether for new applications or for old, difficult-to-maintain monoliths.

To gain an overview of the existing code and the underlying processes, the most important metrics should be analyzed first, such as: 

• cyclomatic complexity,
• nesting depth,
• test coverage,
• file sizes and
• the number of functions and classes.

Large and complex files can be an initial indication of code that is difficult to understand and modify.

This analysis makes it possible to view the applications in isolation and make further decisions. In this step, it should also be clarified which quality assurance processes, such as code reviews, already exist.

Based on the information from the previous step, a decision is made as to which parts of the code should be restructured as a priority or as part of daily work. Transparency is crucial here: it is not important how the code arrived at its current form, but how the existing problems can be solved.

Prioritisation is followed by integration. It is important to note that refactoring is most effective when integrated into daily development work. This includes:

• implementation,
• debugging and
• testing.

However, every rule has its exceptions: particularly incomprehensible or complex code passages must be isolated and restructured separately. The areas affected by this have already been identified during prioritisation.

A major challenge in software refactoring is not to change the existing functionality of the code. To achieve this, you need good test coverage to check the functionality before and after refactoring. This process can be perceived as additional effort, but in fact it is simply an important part of quality assurance in code refactoring.

Once the scope has been defined, all affected code sections are systematically rather than incrementally, i.e. step by step, revised. Only once these isolated code sections have been successfully restructured is the remaining code tackled.

Refactoring improves code quality and maintainability, but it comes with specific challenges. The decision to refactor requires a trade-off between short-term development speed and long-term stability.

The most common challenges in practice are:

• Preserving functionality: The greatest technical difficulty lies in making massive changes to the internal structure without affecting the external behavior of the software.
• Testing effort: Comprehensive test coverage is essential to rule out regression errors. Often, tests must be written before the actual refactoring can begin.
• Merge conflicts: Extensive restructuring in separate branches increases the risk of complex conflicts when merging code, which delays reintegration.
• Delayed visibility: The benefits of refactoring (e.g., faster maintenance) often only become apparent after a delay. This makes it difficult for stakeholders to accept, as no direct functional changes are visible.
• Resource commitment: Successful refactoring requires experienced developers who can identify dependencies in the code. These resources are often lacking in day-to-day operations for new features.