Maxi ContieriEvery developer compares attributes equally. They are mistaken.
TL;DR: Don't export and compare, just compare.
Problems
Encapsulation break
Code Duplication
Information Hiding Violation
Anthropomorphism violation
Solutions
- 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.
