Differences between Code Smells and Anti-patterns

Quite often, developers use the terms like Code smell and anti-pattern interchangeably to indicate some problem in the source code. As if both the terms are each other’s synonyms. However, there are many fundamental differences between both terms. This blog aims at clarifying both terminologies once it for all.

The term “Code Smell” was coined by Kent Beck (Creator of XP programming) while working on Martin Flower’s “Refactoring: Improving the Design of Existing Code” book. A code smell is an indication of something is wrong with the code. E.g., Duplicate Code, Large class, or Lazy class. Design smells and Architecture Smells followed the term Code smell to indicate a deeper problem at the respective abstraction level.

Inspired by Gang of Four design patterns, Andrew Koenig introduced the term anti-patterns to the world. Anti-patterns became a buzzword after the book “AntiPatterns: Refactoring Software, Architectures, and Projects in Crisis” was published by William Brown. According to Brown, “Anti-patterns describe a commonly occurring solution to a problem that generates decidedly negative consequences. “ Software development is a complicated process, and failures are part of life. Many decisions may lead you to failure. So, it is crucial to capture those decisions or processes using pattern language. (Of course, there is a pattern to Madness as well ). These patterns can guide future software engineers, managers, and learners on what to avoid. Anti-patterns allow developers to learn from other’s mistakes. Design patterns talk about a reusable solution for recurring problems, and anti-patterns are focused on negative consequences. Anti-patterns can act as a useful tool for communication between the developers.
E.g., Blob anti-pattern -if a class has tons of responsibilities than other classes, such class becomes difficult to reuse, maintain, and test.

Now that we understood what both terms are, let us see the differences between them:

1. The most basic difference between Code smell and anti-pattern is the Context. Anti-patterns belong to the Pattern universe. We use the anti-pattern term in the context of describing patterns that lead to some kind of negative consequence. A code smell is used in the context of hint and not patterns.
2. That brings us to the second difference. A code smell is a hint. It may or may not be a problem. It is subjective as well. Meaning that it is biased towards the analyzer’s perspective, experience, knowledge, and thinking process. If I say I “feel” XYZ might be the problem then it is not necessary that XYZ must be a problem. In contrast, Anti-patterns are the patterns that tell you if you don’t follow XYZ, it is certain that you are approaching disaster. It is backed by historical evidence/experience captured in the semi-formal language (Pattern specification language).
3. Code smells are described using natural language (plain English). That’s why code smells can be deceiving and depend on how analyzers interpret them. Anti-patterns are published in structured semi-formal Pattern Specification Language after careful reviews. So, they are more formal than code smells. To keep them useful for the general audience (not everyone is a mathematician or scientist), anti-patterns are not published using mathematical formal languages.
4. Code smells are easier to spot (That’s why the term includes the word smell). E.g., Duplicate Codes, Excessive use of Switch cases in the code. However, anti-patterns may or may not be easier to spot. Depends on the anti-pattern problem. E.g., Cargo cult programming- Using code without understanding why. How will you spot this in the code?.
5. Code smells are restricted to software problems only. Anti-patterns are broader than the code smell. For example, Anti-patterns are not only used in describing the commonly occurring solution to software problems but also process problems, organizational, or configurational problems. The use of Anti-patterns can be extended or molded to capture more different kinds of problems. E.g., Analysis Paralysis — Overthinking or overanalyzing the problem can paralyze the decision-making process. (Organizational anti-pattern).
6. There can be an overlapping between code smell and anti-pattern. E.g., the blob/God class anti-pattern tells you that if the class has tons of responsibilities, code maintenance for that class will be difficult. It is similar to the Large Class/ God Object code smell. However, the purpose behind the anti-pattern is to discuss the pattern leading to negative consequences formally. The Code smell is a “feel” that there can be a problem with the code.

These are some key differences among the code smells and anti-patterns. I hope this article clarifies both terminologies.