Refactoring for Software Design Smells Managing Technical Debt (2014)¶

“Refactoring for Software Design Smells: Managing Technical Debt” by Girish Suryanarayana, Ganesh Samarthyam, and Tushar Sharma (2014) is a comprehensive guide to identifying, analyzing, and addressing design issues in software systems, often referred to as “design smells” or “code smells.” The book aims to help developers improve the quality and maintainability of their software by providing techniques for refactoring code to eliminate these smells and manage technical debt.

“Smells”, aka technical debt¶

The book begins by discussing the concept of technical debt and its impact on software projects. It then introduces 25 design smells, organized into four categories: foundational, creational, structural, and behavioral smells. For each smell, the authors provide detailed descriptions, examples, and explanations of the underlying design issues.

Here are some of the main design smells identified in each category:

Foundational Smells:
- Deficient Encapsulation: Insufficient protection of the internal state or behavior of a class or module.
- Unexploited Encapsulation: Failing to utilize the benefits of encapsulation, such as hiding implementation details and reducing coupling.
- Broken Modularization: Poor organization of modules, leading to tightly coupled, difficult-to-maintain systems.
- Cyclic Dependencies: Circular dependencies between classes or modules, which can make the system harder to understand and maintain.
Creational Smells:
- Unstable Dependency: Dependencies on unstable or frequently changing modules, which can lead to ripple effects throughout the system.
- Violation of the Law of Demeter: Overly complex and indirect communication between objects, leading to increased coupling and reduced modularity.
- Disobeyed Encapsulation: Bypassing the proper encapsulation of a class or module, leading to increased coupling and reduced maintainability.
Structural Smells:
- Hub-like Modularization: A module that excessively depends on or is depended upon by other modules, creating a central point of coupling in the system.
- Insufficient Modularization: Failing to divide the system into sufficiently small and cohesive modules, leading to poor separation of concerns.
- Ambiguous Interface: Unclear or unintuitive interfaces, which can make the system more challenging to understand and use.
- Feature Envy: A situation where a module excessively uses or depends on the features of another module, indicating poor cohesion and potential design problems.
Behavioral Smells:
- Inappropriate Intimacy: A close relationship between two classes or modules that should not be tightly coupled, leading to increased complexity and reduced maintainability.
- Indecent Exposure: Exposing more information or functionality than necessary, violating the principle of information hiding and increasing coupling.
- Uncommunicative Name: Poorly named classes, methods, or variables that do not clearly convey their purpose or responsibilities.
- Shotgun Surgery: A change in the system that requires modifications to multiple modules, indicating a lack of cohesion and poor separation of concerns.

These design smells, along with others identified in the book, serve as indicators of potential design problems in a software system. By recognizing and addressing these smells, developers can improve the quality, maintainability, and modularity of their software, effectively managing technical debt.

Refactoring techniques¶

The main part of the book focuses on refactoring techniques to address design smells. The authors present over 60 refactoring strategies, accompanied by practical examples and step-by-step guidance. The book also offers insights into the relationship between design smells and software quality attributes, such as performance, robustness, and modifiability.

Some of the main refactoring techniques described in the book include:

Encapsulate Field: Improve encapsulation by making a field private and providing public getter and/or setter methods to access and modify it.
Extract Class: If a class has multiple responsibilities, create a new class and move the related methods and fields to the new class to improve cohesion and separation of concerns.
Extract Method: If a method is too long or complex, create a new method containing part of the original method’s functionality and call it from the original method. This improves readability and maintainability.
Inline Method: If a method’s functionality is too simple or used only once, consider merging its content with the calling method to reduce unnecessary complexity.
Move Method: If a method is more closely related to another class than the one it currently belongs to, move the method to that class to improve cohesion and reduce coupling.
Pull Up Method: If two or more subclasses have identical methods, move the method to the superclass to eliminate code duplication and improve maintainability.
Push Down Method: If a method in a superclass is only relevant to a specific subclass, move the method to that subclass to improve cohesion and modularity.
Rename Method: If a method’s name is unclear or does not accurately represent its purpose, rename it to improve readability and maintainability.
Replace Inheritance with Delegation: If a subclass is using inheritance primarily for code reuse, consider replacing it with delegation by creating an instance of the superclass and forwarding method calls to it.
Replace Conditional with Polymorphism: If a method contains several conditional statements to determine the behavior based on the object’s type, consider using polymorphism by creating subclasses for each type and implementing the method in each subclass.

“Refactoring for Software Design Smells” is a valuable resource for software developers, architects, and technical leads seeking to improve the quality and maintainability of their software systems. By understanding and addressing design smells, developers can manage technical debt more effectively and create software that is easier to maintain, evolve, and understand.

Refactoring for Software Design Smells Managing Technical Debt (2014)¶

“Smells”, aka technical debt¶

Refactoring techniques¶

See also¶