Code Smell 46 — Repeated Code

DRY is our mantra. Teachers tell us to remove duplication. We need to go beyond.

Photo by Sid Balachandran on Unsplash

Problems

• Code Duplication
• Maintainability
• Don’t Repeat Yourself

Solutions

1. Find repeated patterns (not repeated code).
2. Create an abstraction.
3. Parametrize abstraction calls.
4. Use composition and never inheritance.
5. Unit test new abstraction.

Sample Code

Wrong

Right

Detection

Linters can find repeated code.

There are not very good finding similar patterns.

Maybe soon machine learning will help us find such abstractions automatically.

For now, it is up to us, humans.

Examples

• Automatic Code Generators

Tags

• Duplication

Conclusion

Repeated code is always a smell.

Copying and pasting code is always a shame.

With our refactoring tools, we need to accept the duplication remove challenge trusting our tests as a safety net.

Relations

Code Smell 11 — Subclassification for Code Reuse

More info

DRY - Don't repeat yourself

Laziness II: Code Wizards

Copy and paste is a design error.

David Parnas

Software Engineering Great Quotes

This article is part of the CodeSmell Series.

How to Find the Stinky parts of your Code