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
- 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
Refactorings
More Info
Disclaimer
Code Smells are just my opinion.
Credits
Photo by Noah Buscher on Unsplash
A complex system that works is invariably found to have evolved from a simple system that worked.
John Gall
This article is part of the CodeSmell Series.
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