Code Smell 150 - Equal Comparison

Photo by Piret Ilver on Unsplash

Code Smell 150 - Equal Comparison

Every developer compares attributes equally. They are mistaken.

Maxi Contieri
·Jul 19, 2022·

2 min read

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Table of contents

  • Problems
  • Solutions
  • Context
  • Sample Code
  • Detection
  • Tags
  • Conclusion
  • Relations
  • Credits

TL;DR: Don't export and compare, just compare.

Problems

  • Encapsulation break

  • Code Duplication

  • Information Hiding violation

  • Anthropomorphism violation

Solutions

  1. Hide the comparison in a single method

Context

Attribute comparison is heavily used in our code.

We need to focus on behavior and responsibilities.

It is an object's responsibility to compare with other objects. Not our own.

Premature Optimizers will tell us this is less performant.

We should ask them for real evidence and contrast the more maintainable solution.

Sample Code

Wrong

if (address.street == 'Broad Street') {


if (location.street == 'Bourbon St') {

// 15000 usages in a big system  
// Comparisons are case sensitive

Right

if (address.isAtStreet('Broad Street') {
    }

// ...

if (location.isAtStreet('Bourbon St') {
    }  
// 15000 usages in a big system  

function isAtStreet(street) {
  // We can change Comparisons to case sensitive in just one place. 
}

Detection

[X] Semi-Automatic

We can detect attribute comparison using syntax trees.

There can be good uses for primitive types as with many other smells.

Tags

  • Encapsulation

Conclusion

We need to put responsibilities in a single place.

Comparing is one of them.

If some of our business rules change we need to change a single point.

Relations

Credits

Photo by Piret Ilver on Unsplash


Behavior is the most important thing about software. It is what users depend on. Users like it when we add behavior (provided it is what they really wanted), but if we change or remove behavior they depend on (introduce bugs), they stop trusting us.

Michael Feathers


This article is part of the CodeSmell Series.

 
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Technical Opinions are my own. I don't have the revealed truth.

Software Design is a creative activity. These are hints and not rigid rules.

I write on BackEnd Business Systems and OOP Design. My advice/experience might not suit other systems.

You can write me at info(at)maximilianocontieri.com