Code Smell 158 - Variables not Variable

You assign a value to a variable and use it, but never change it

TL;DR: Be declarative on mutability.

Problems

• Readability

• Honor the Bijection mutability.

• Potential performance and memory issues.

Solutions

1. Change the variable to a constant and be clear on its scope

Context

We are always learning from the domain.

Sometimes we guess that a value can change with the MAPPER.

Later on, we learn it won't change.

Therefore we need to promote it to a constant.

This will also avoid Magic Constants

Sample Code

Wrong

<?php

function configureUser() {
  $password = '123456';
  // Setting a password on a variable is another vulnerability
  // And Code Smell
  $user = new User($password);
  // Notice Variable doesn't change
}

Right

<?php

define("USER_PASSWORD", '123456')

function configureUser() {  
  $user = new User(USER_PASSWORD);
}

// or 

function configureUser() {  
  $user = new User(userPassword());
}

function userPassword() : string {
  return '123456';
}

// Case is oversimplification as usual

Detection

[X] Automatic

Many linters check if the variable has just one assignment.

We can also perform mutation testing and try to modify the variable to see if tests break.

Tags

• Mutability

Conclusion

We must challenge ourselves and refactor when the variable scope is clear and we learn more about its properties and mutability.

Relations

Code Smell 127 - Mutable Constants

Maxi Contieri ・ Apr 5 '22

#tutorial #webdev #javascript #beginners

Code Smell 107 - Variables Reuse

Maxi Contieri ・ Dec 1 '21

#oop #programming #webdev #tutorial

Code Smell 02 - Constants and Magic Numbers

Maxi Contieri ・ Oct 21 '20

#beginners #codenewbie #100daysofcode #codequality

Refactorings

Refactoring 003 - Extract Constant

Maxi Contieri ・ Jan 2 '22

#oop #programming #refactoring #cleancode

More Info

The evil powers of mutants

Maxi Contieri ・ Dec 19 '20

#webdev #programming #mutation #oop

Disclaimer

Code Smells are just my opinion.

Credits

Photo by Noah Buscher on Unsplash

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A complex system that works is invariably found to have evolved from a simple system that worked.

John Gall

Software Engineering Great Quotes

Maxi Contieri ・ Dec 28 '20

#codenewbie #programming #quotes #software

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This article is part of the CodeSmell Series.

How to Find the Stinky parts of your Code

Maxi Contieri ・ May 21 '21

#codenewbie #tutorial #codequality #beginners