How to Recognize and Refactor Code Smells - A Developer’s Guide

Developers often come across code smells in their work. We all understand that they aren't bugs but rather signals that something isn't quite right in the code. These indicators are referred as "code smells" in the developer community.

Every engineer has faced this scenario, - staring at these code smells while juggling tight deadlines and feature requests. The big question always lingers: :) do we take the time to clean up the code and refactor, or do we push ahead to meet business demands? It’s a constant struggle - balancing clean, maintainable code with the pressure to ship fast.

But ignoring code smells today leads to complicated code problems later.

This guide explores Code Smells and effective strategies for resolving them.

Code Smells That Demand Your Attention

We often come across some major types of code smells that require refactoring.

Let us start with Bloaters.

Bloaters:

Bloaters are code structures that have grown too large and complex appearing in three main forms:

1. Large Classes: Classes handling too many responsibilities

2. Long Methods: Functions with excessive lines of code

3. Long Parameter Lists: Methods with too many parameters

It usually starts with, just one more feature, a quick bug fix, we will refactor later excuses. At first, it seems harmless. But over time, these small additions pile up.

Suddenly, you will be staring at a 500-line class or method, handling database queries, business logic, and UI rendering—all in one place.

Solution for the bloaters is simple, break the bigger one into smaller.

Is Your Code Bloating? Check Below.

Ask yourself these questions to spot bloated code in your project:

If you’re nodding yes to any of these, then your code is bloating and its probably time to refactor. A little cleanup now will save you a ton of trouble later.

1. Large Class (God Class)

A large class has too many methods and lines of code, trying to handle multiple tasks all in one place. Below is an example of a large class that includes different methods, each responsible for a separate function.

The problem?

• The class mixes profile management, account processing, and notifications thereby violating the Single Responsibility Principle.

• New feature requests will add to the class’s size, further bloating the code.

• A change in one method can cause another method to fail because of the data dependencies.

• Testing becomes harder as all functionality residing in a single class.

Refactoring Method: Break the Large class into focused smaller classes with methods that handle specific functionalities.

2. Long Methods

A method with excessive lines of code is a sign of poor design, simply put If you're scrolling through a method just to read all its lines, it's too long and considered as a code smell.

In the snippet below, analyze_sales_data handles everything, from reading the CSV file and converting values to computing statistics and preparing output. While this might seem convenient at first, having all these responsibilities in one place quickly makes the code harder to maintain, test, and modify.

The Problem?

• Having all logic in one function makes the code difficult to follow.

• Altering any part of the function can break other features as it is tightly coupled.

• You can’t test a single functionality in isolation because everything is merged into one block.

Refactoring Method: Break down the larger function into smaller helper functions.

3. Long Parameter List

Long Parameter List occurs when a function demands many parameters.

Note: - Anything more than four parameters is often a sign of code smell.

Below is a simple example illustrating this code smell in action. Notice how create_order demands a long list of parameters, making the function’s signature complicated and harder to work with.

The problem?

• A long parameter list makes the function’s signature complex and hard to read.

• It’s easy to mix up the order of arguments or pass in the wrong types.

• Any change in the parameter list forces updates in multiple places.

Refactoring Method: Use request objects instead of long parameter lists. Group related values into a single object, it makes function calls cleaner and easier to extend later.

Note: - If you move just the data fields to a new class without including any behaviors or methods that operate on that data, you're creating a code smell named Data Class - which we will see in the upcoming section.

4. Data Clumps:

A Data Clump is when the same group of variables appear together in multiple places. If you see the same 2-4 data items appearing together across multiple classes or methods, it's likely a Data Clump.

The problem?

• Changes to the data field require updates in multiple places.

• Code becomes harder to maintain with repeated parameter groups

Refactoring Method: Extract related parameters into their own class. This organizes related data and reduces duplication across your codebase. Both Parameter Bloat and Data Clumps can be solved by extracting related data into their own classes.

Object-Oriented Abusers:

When OOP principles are misused, they can add unnecessary complexity to the code. Overusing inheritance, violating encapsulation, and creating tightly coupled dependencies often lead to what we call Object-Oriented Abusers.

1. Refused Bequest:

A Refused Bequest happens when a child class extends a parent class but doesn’t need most of its inherited properties or methods.

Instead of forcing inheritance, it's better to use smaller, focused classes to keep the code simple, flexible, and easy to maintain.

In the snippet below, the child classes inherit all methods from OnlinePaymentMethod but have no need for handle_card_details(), and therefore raise NotImplementedError when it’s called.

Problem:

• This leads to unused methods, forced overrides (e.g., NotImplementedError), and makes the inheritance structure more complex to maintain.

Refactoring Method: The solution creates smaller, more focused interfaces, such as BaseOnlinePayment for generic processing and CardPaymentSupport for card handling. This way, child classes like PayPalPayment and CryptoPayment inherit only what they need and avoiding irrelevant methods.

2. Temporary Field

A Temporary Field is a class variable that only serves a purpose in one or two methods. Such variables should be moved into the specific methods where they're used, rather than keeping them unnecessarily at the class level.

Here, temp_discount is stored as a class field, even though it's used only in one method.

Refactoring Method: Instead of keeping temp_discount as a class-level field move it directly into the method where it's actually used. This improves encapsulation by restricting the variable's scope to just where it's needed.

3. DataClass:

A Data Class is a class that mainly holds data fields and has few or no methods, similar to an Anemic Domain Model. Some developers prefer this, but it often leads to procedural code and scattered logic.

Anemic Model: Classes that only hold data without any behavior. Instead of having methods inside the class to process the data, all the operations are done outside or in separate service classes.

Below is the code explaining the Data Class Code Smell. The Person class simply holds data while the actual logic (tax and bonus calculations) lives outside the class

Refactoring Method: Below is the refactored code which encapsulates behavior within the class, making it a proper class than just a data holder.

Dispensable:

Unnecessary or redundant code makes the codebase harder to read and maintain. Dead code, duplicate logic, unnecessary classes, and excessive comments fall under this category.

1. Dead Code:

Unused code, old methods, and unnecessary variables that no longer serve a purpose should be removed to keep the code clean and maintainable.

Refactoring Method: Delete unused methods or classes.

2. Duplicate Code

When the same logic appears in multiple places, maintaining the code becomes difficult.

Refactoring Method: Extract common functionality into reusable functions or classes to follow the DRY (Don’t Repeat Yourself) principle.

3. Lazy Class

A class with only one or two methods that adds little value should be merged into another class instead of keeping unnecessary abstraction.

4. Noisy Comments

Excessive comments explaining what the code does rather than why it exists can be distracting. If simple logic requires comments, the code might need refactoring.

Refactoring Method: Keep comments meaningful and remove those that state the obvious.

Note: - A Good Code should be self-explanatory.

Couplers

When classes or methods rely too much on each other, changing one thing can break multiple parts of the system

1. Feature Envy

A method in one class frequently accesses data or methods from another class, instead of its own class.

Refactoring Method: Group related data and functionality together. If a class or method primarily relies on another class’s data or behavior, relocate it to that class.

When a method clearly belongs in another class, move the entire method to that class (Move Method). If only part of a method depends on external data, extract just that part into a separate method (Extract Method) and add it to the right class.

2. Inappropriate Intimacy

If method of one class depends on internal variables of another class, then it is called as Inappropriate Intimacy.

The difference between Feature Envy and Inappropriate Intimacy is that Feature Envy uses too many public methods of another class, while Inappropriate Intimacy violates encapsulation by directly accessing private members of another class.

3. Message Chain:

Message chain occur when functions navigate through multiple class dependencies to retrieve a final value, creating a chain like below.

invoice = order_processor.get_order(order_id).get_items().calculate_total().apply_discount().generate_invoice()  

Client code directly calls multiple objects in sequence, making it dependent on the entire object structure.

Refactoring Method: Encapsulate the chain behind a single method. Client only sees what it needs, internal structure can be changed freely.

4. Middle Man:

To fix the Message Chain, developers often introduce a service class (Middle Man) to handle the chain of operations. However, if this new class simply forwards calls without adding business logic, it becomes a Middleman.

In this example, OrderService class (Middle Man) is introduced to address the Message Chain issue we saw above, but it simply forwards the method calls (order.getItems().getTotal().applyDiscount()) without adding any real logic.

class OrderService:
    def process_order(self, order):
        # Just forwards the chain without adding value
        return order.getItems().getTotal().applyDiscount()

Refactoring Method: Remove the OrderService middleman to let OrderProcessor class work directly with Invoice class.

Change Preventers

These code smells show up when a single modification in one part of the system triggers a chain reaction of changes in other parts. As a result, even small updates can become complicated and expensive to implement.

1. Divergent Change

This occurs when you need to modify multiple, unrelated methods in a single class to accommodate a new feature or requirement.

When one class needs updates for database changes, UI updates, and API modifications, it violates Single Responsibility Principle. Each class should have one reason to change, making code maintenance predictable.

Refactoring Method: Separate functionalities into different classes.

2. Shotgun Surgery

One modification force changes across multiple classes. For example, adding a new user field requires updates to User, Profile, Authentication, and Database classes. This tight coupling makes changes risky and time-consuming.

Note: - Divergent Change and Shotgun Surgery represent inverse patterns in how changes propagate through code - many changes to one class versus one change to many classes.

Refactoring Method: For Shotgun Surgery, extract the class with common functionalities and apply changes only to that class.

3. Parallel Inheritance Hierarchies

When you create a class in one hierarchy, you're compelled to create a corresponding class in others. This violates DRY and makes changes exponentially complex.

Refactoring Method: Combine the hierarchies.

Refactoring Techniques

We've explored common code smells and their refactoring solutions. Each smell may require different approaches, and often combining multiple techniques yields the best results. In the following section, we'll examine essential refactoring patterns that every developer should master to maintain clean, maintainable code.

1. Composing Methods

2. Simplifying Methods

3. Abstraction Methods

Composing Methods:

Simplifying Methods:

Abstraction Methods:

Code Smell: Refactoring Vs No Action

Now that we’ve looked at code smells and how to refactor them, what if we don’t address these issues?

This diagram shows the impact of not taking action.

Conclusion:

Every developer will come across code smells, whether or not they're aware of them. By understanding these issues and learning how to refactor them, you can maintain a clean and scalable codebase and become a more skilled developer in the process. This blog lays the foundation for recognizing and addressing code smells effectively.

Alternatively, in today’s world, you can use an AI Code Reviewer or a VSCode Extension to help you review code and have a senior programmer on the side to help you give the necessary advice.

Hope you found this guide on Code Smell and Refactoring valuable.

Happy Coding!